Hey everyone. I've had this problem since Windows Vista. I did a clean install with Windows 7 and hoped it would fix the problem. Also swapped out the video card just to rule out a strange driver issue.

Here's what's happening. After running for some period of time (usually a few hours), the Start button/orb will loose it's "Chrome" and turn into a plain button that just says "Start." It will work fine for a while, but then the start menu will just stop showing. Additionally, when I hit Win+D to show the desktop, the entire taskbar completely disappears.

I can get it back usually by moving/minimizing windows that may be overlapping where the start menu should show. Otherwise, it requires either a full reboot or I'll end up killing & restarting the explorer.exe process.

I realize that this is a strange issue - I took a video of it http://www.youtube.com/watch?v=0B3WwT0uyr4

Thanks!

--Edit-- Here's my HijackThis log:

Logfile of Trend Micro HijackThis v2.0.3 (BETA)
Scan saved at 4:19:00 PM, on 12/16/2009
Platform: Unknown Windows (WinNT 6.01.3504)
MSIE: Internet Explorer v8.00 (8.00.7600.16385)
Boot mode: Normal

Running processes:
C:\Program Files (x86)\Pantone\hueyPRO\hueyPROTray.exe
C:\Program Files (x86)\Adobe\Acrobat 9.0\Acrobat\acrotray.exe
C:\Program Files (x86)\iTunes\iTunesHelper.exe
C:\Program Files (x86)\Java\jre6\bin\jusched.exe
C:\Program Files (x86)\MagicDisc\MagicDisc.exe
C:\Program Files (x86)\Trillian\trillian.exe
C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\IDE\devenv.exe
C:\Program Files (x86)\Microsoft SQL Server\100\Tools\Binn\VSShell\Common7\IDE\Ssms.exe
C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\IDE\devenv.exe
C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\IDE\devenv.exe
C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\IDE\devenv.exe
C:\Program Files (x86)\Common Files\Microsoft Shared\DevServer\9.0\WebDev.WebServer.EXE
C:\Program Files (x86)\Notepad++\notepad++.exe
C:\Program Files (x86)\Fiddler2\Fiddler.exe
C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\IDE\mspdbsrv.exe
C:\Program Files (x86)\iTunes\iTunes.exe
C:\Program Files (x86)\Adobe\Adobe Illustrator CS4\Support Files\Contents\Windows\Illustrator.exe
C:\Program Files (x86)\ColorPic 4.1\ColorPic.exe
C:\Program Files (x86)\Adobe\Acrobat 9.0\Acrobat\Acrobat.exe
C:\Program Files (x86)\Common Files\Microsoft Shared\Help 9\dexplore.exe
C:\Program Files (x86)\Common Files\Microsoft Shared\Help 9\dexplore.exe
C:\Program Files (x86)\Internet Explorer\IEXPLORE.EXE
C:\Program Files (x86)\Internet Explorer\IEXPLORE.EXE
C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\IDE\devenv.exe
C:\Program Files (x86)\eBay\Blackthorne\bin\BT.exe
C:\Program Files (x86)\Internet Explorer\IEXPLORE.EXE
C:\Program Files (x86)\CamStudio\Recorder.exe
C:\Program Files (x86)\CamStudio\Playplus.exe
C:\Program Files (x86)\Mozilla Firefox 3.6 Beta 3\firefox.exe
C:\Program Files (x86)\CamStudio\Playplus.exe
C:\Program Files (x86)\PuTTY\putty.exe
C:\Program Files (x86)\CamStudio\Playplus.exe
C:\Program Files (x86)\CamStudio\Playplus.exe
C:\Program Files (x86)\TrendMicro\HiJackThis\HiJackThis.exe
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Page = http://go.microsoft.com/fwlink/?LinkId=54896
R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://go.microsoft.com/fwlink/?LinkId=69157
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = http://go.microsoft.com/fwlink/?LinkId=69157
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Search_URL = http://go.microsoft.com/fwlink/?LinkId=54896
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Search Page = http://go.microsoft.com/fwlink/?LinkId=54896
R0 - HKLM\Software\Microsoft\Internet Explorer\Main,Start Page = http://go.microsoft.com/fwlink/?LinkId=69157
R0 - HKLM\Software\Microsoft\Internet Explorer\Search,SearchAssistant = 
R0 - HKLM\Software\Microsoft\Internet Explorer\Search,CustomizeSearch = 
R0 - HKLM\Software\Microsoft\Internet Explorer\Main,Local Page = C:\Windows\SysWOW64\blank.htm
R0 - HKCU\Software\Microsoft\Internet Explorer\Toolbar,LinksFolderName = 
F2 - REG:system.ini: UserInit=userinit.exe
O2 - BHO: ContributeBHO Class - {074C1DC5-9320-4A9A-947D-C042949C6216} - C:\Program Files (x86)\Adobe\/Adobe Contribute CS4/contributeieplugin.dll
O2 - BHO: AcroIEHelperStub - {18DF081C-E8AD-4283-A596-FA578C2EBDC3} - C:\Program Files (x86)\Common Files\Adobe\Acrobat\ActiveX\AcroIEHelperShim.dll
O2 - BHO: Groove GFS Browser Helper - {72853161-30C5-4D22-B7F9-0BBC1D38A37E} - C:\PROGRA~2\MICROS~1\Office14\GROOVEEX.DLL
O2 - BHO: Windows Live Sign-in Helper - {9030D464-4C02-4ABF-8ECC-5164760863C6} - C:\Program Files (x86)\Common Files\Microsoft Shared\Windows Live\WindowsLiveLogin.dll
O2 - BHO: Adobe PDF Conversion Toolbar Helper - {AE7CD045-E861-484f-8273-0445EE161910} - C:\Program Files (x86)\Common Files\Adobe\Acrobat\ActiveX\AcroIEFavClient.dll
O2 - BHO: URLRedirectionBHO - {B4F3A835-0E21-4959-BA22-42B3008E02FF} - C:\PROGRA~2\MICROS~1\Office14\URLREDIR.DLL
O2 - BHO: Java(tm) Plug-In 2 SSV Helper - {DBC80044-A445-435b-BC74-9C25C1C588A9} - C:\Program Files (x86)\Java\jre6\bin\jp2ssv.dll
O2 - BHO: SmartSelect - {F4971EE7-DAA0-4053-9964-665D8EE6A077} - C:\Program Files (x86)\Common Files\Adobe\Acrobat\ActiveX\AcroIEFavClient.dll
O3 - Toolbar: Adobe PDF - {47833539-D0C5-4125-9FA8-0819E2EAAC93} - C:\Program Files (x86)\Common Files\Adobe\Acrobat\ActiveX\AcroIEFavClient.dll
O3 - Toolbar: Contribute Toolbar - {517BDDE4-E3A7-4570-B21E-2B52B6139FC7} - C:\Program Files (x86)\Adobe\/Adobe Contribute CS4/contributeieplugin.dll
O4 - HKLM\..\Run: [AdobeCS4ServiceManager] "C:\Program Files (x86)\Common Files\Adobe\CS4ServiceManager\CS4ServiceManager.exe" -launchedbylogin
O4 - HKLM\..\Run: [Adobe Acrobat Speed Launcher] "C:\Program Files (x86)\Adobe\Acrobat 9.0\Acrobat\Acrobat_sl.exe"
O4 - HKLM\..\Run: [Acrobat Assistant 8.0] "C:\Program Files (x86)\Adobe\Acrobat 9.0\Acrobat\Acrotray.exe"
O4 - HKLM\..\Run: [Adobe_ID0ENQBO] C:\PROGRA~2\COMMON~1\Adobe\ADOBEV~1\Server\bin\VERSIO~2.EXE
O4 - HKLM\..\Run: [QuickTime Task] "C:\Program Files (x86)\QuickTime\QTTask.exe" -atboottime
O4 - HKLM\..\Run: [iTunesHelper] "C:\Program Files (x86)\iTunes\iTunesHelper.exe"
O4 - HKLM\..\Run: [SunJavaUpdateSched] "C:\Program Files (x86)\Java\jre6\bin\jusched.exe"
O4 - HKUS\S-1-5-19\..\Run: [Sidebar] %ProgramFiles%\Windows Sidebar\Sidebar.exe /autoRun (User 'LOCAL SERVICE')
O4 - HKUS\S-1-5-19\..\RunOnce: [mctadmin] C:\Windows\System32\mctadmin.exe (User 'LOCAL SERVICE')
O4 - HKUS\S-1-5-20\..\Run: [Sidebar] %ProgramFiles%\Windows Sidebar\Sidebar.exe /autoRun (User 'NETWORK SERVICE')
O4 - HKUS\S-1-5-20\..\RunOnce: [mctadmin] C:\Windows\System32\mctadmin.exe (User 'NETWORK SERVICE')
O4 - Startup: ChatNowDesktop.appref-ms
O4 - Startup: MagicDisc.lnk = C:\Program Files (x86)\MagicDisc\MagicDisc.exe
O4 - Startup: Trillian.lnk = C:\Program Files (x86)\Trillian\trillian.exe
O4 - Global Startup: Digsby.lnk = C:\Program Files (x86)\Digsby\digsby.exe
O4 - Global Startup: hueyPROTray.lnk = C:\Program Files (x86)\Pantone\hueyPRO\hueyPROTray.exe
O4 - Global Startup: OfficeSAS.lnk = ?
O8 - Extra context menu item: Append Link Target to Existing PDF - res://C:\Program Files (x86)\Common Files\Adobe\Acrobat\ActiveX\AcroIEFavClient.dll/AcroIEAppendSelLinks.html
O8 - Extra context menu item: Append to Existing PDF - res://C:\Program Files (x86)\Common Files\Adobe\Acrobat\ActiveX\AcroIEFavClient.dll/AcroIEAppend.html
O8 - Extra context menu item: Convert Link Target to Adobe PDF - res://C:\Program Files (x86)\Common Files\Adobe\Acrobat\ActiveX\AcroIEFavClient.dll/AcroIECaptureSelLinks.html
O8 - Extra context menu item: Convert to Adobe PDF - res://C:\Program Files (x86)\Common Files\Adobe\Acrobat\ActiveX\AcroIEFavClient.dll/AcroIECapture.html
O8 - Extra context menu item: E&xport to Microsoft Excel - res://C:\PROGRA~1\MICROS~1\Office14\EXCEL.EXE/3000
O8 - Extra context menu item: S&end to OneNote - res://C:\PROGRA~1\MICROS~1\Office14\ONBttnIE.dll/105
O9 - Extra button: Send to OneNote - {2670000A-7350-4f3c-8081-5663EE0C6C49} - C:\Program Files (x86)\Microsoft Office\Office14\ONBttnIE.dll
O9 - Extra 'Tools' menuitem: Se&nd to OneNote - {2670000A-7350-4f3c-8081-5663EE0C6C49} - C:\Program Files (x86)\Microsoft Office\Office14\ONBttnIE.dll
O9 - Extra button: OneNote Lin&ked Notes - {789FE86F-6FC4-46A1-9849-EDE0DB0C95CA} - C:\Program Files (x86)\Microsoft Office\Office14\ONBttnIELinkedNotes.dll
O9 - Extra 'Tools' menuitem: OneNote Lin&ked Notes - {789FE86F-6FC4-46A1-9849-EDE0DB0C95CA} - C:\Program Files (x86)\Microsoft Office\Office14\ONBttnIELinkedNotes.dll
O9 - Extra button: Fiddler2 - {CF819DA3-9882-4944-ADF5-6EF17ECF3C6E} - "C:\Program Files (x86)\Fiddler2\Fiddler.exe" (file missing)
O9 - Extra 'Tools' menuitem: Fiddler2 - {CF819DA3-9882-4944-ADF5-6EF17ECF3C6E} - "C:\Program Files (x86)\Fiddler2\Fiddler.exe" (file missing)
O13 - Gopher Prefix: 
O16 - DPF: {5554DCB0-700B-498D-9B58-4E40E5814405} (RSClientPrint 2008 Class) - http://reportserver/Reports/Reserved.ReportViewerWebControl.axd?ReportSession=oxadkhfvfvt1hzf2eh3y1ay2&ControlID=b89e27f15e734f3faee1308eebdfab2a&Culture=1033&UICulture=9&ReportStack=1&OpType=PrintCab&Arch=X86
O16 - DPF: {82774781-8F4E-11D1-AB1C-0000F8773BF0} (DLC Class) - https://transfers.ds.microsoft.com/FTM/TransferSource/grTransferCtrl.cab
O16 - DPF: {D27CDB6E-AE6D-11CF-96B8-444553540000} (Shockwave Flash Object) - http://fpdownload2.macromedia.com/get/shockwave/cabs/flash/swflash.cab
O17 - HKLM\System\CCS\Services\Tcpip\Parameters: Domain = LapkoSoft.local
O17 - HKLM\System\CCS\Services\Tcpip\..\{5992B87A-643B-4385-A914-249B98BF7129}: NameServer = 192.168.1.10
O17 - HKLM\System\CS1\Services\Tcpip\Parameters: Domain = LapkoSoft.local
O17 - HKLM\System\CS2\Services\Tcpip\Parameters: Domain = LapkoSoft.local
O18 - Filter hijack: text/xml - {807573E5-5146-11D5-A672-00B0D022E945} - C:\Program Files (x86)\Common Files\Microsoft Shared\OFFICE14\MSOXMLMF.DLL
O23 - Service: Adobe Version Cue CS4 - Adobe Systems Incorporated - C:\Program Files (x86)\Common Files\Adobe\Adobe Version Cue CS4\Server\bin\VersionCueCS4.exe
O23 - Service: @%SystemRoot%\system32\Alg.exe,-112 (ALG) - Unknown owner - C:\Windows\System32\alg.exe (file missing)
O23 - Service: Apple Mobile Device - Apple Inc. - C:\Program Files (x86)\Common Files\Apple\Mobile Device Support\bin\AppleMobileDeviceService.exe
O23 - Service: ASP.NET State Service (aspnet_state) - Unknown owner - C:\Windows\Microsoft.NET\Framework\v2.0.50727\aspnet_state.exe (file missing)
O23 - Service: Bonjour Service - Apple Inc. - C:\Program Files (x86)\Bonjour\mDNSResponder.exe
O23 - Service: @%SystemRoot%\system32\efssvc.dll,-100 (EFS) - Unknown owner - C:\Windows\System32\lsass.exe (file missing)
O23 - Service: @%systemroot%\system32\fxsresm.dll,-118 (Fax) - Unknown owner - C:\Windows\system32\fxssvc.exe (file missing)
O23 - Service: FLEXnet Licensing Service - Acresso Software Inc. - C:\Program Files (x86)\Common Files\Macrovision Shared\FLEXnet Publisher\FNPLicensingService.exe
O23 - Service: FLEXnet Licensing Service 64 - Acresso Software Inc. - C:\Program Files\Common Files\Macrovision Shared\FLEXnet Publisher\FNPLicensingService64.exe
O23 - Service: @%windir%\system32\inetsrv\iisres.dll,-30007 (IISADMIN) - Unknown owner - C:\Windows\system32\inetsrv\inetinfo.exe (file missing)
O23 - Service: iPod Service - Apple Inc. - C:\Program Files\iPod\bin\iPodService.exe
O23 - Service: @keyiso.dll,-100 (KeyIso) - Unknown owner - C:\Windows\system32\lsass.exe (file missing)
O23 - Service: @comres.dll,-2797 (MSDTC) - Unknown owner - C:\Windows\System32\msdtc.exe (file missing)
O23 - Service: @%SystemRoot%\System32\netlogon.dll,-102 (Netlogon) - Unknown owner - C:\Windows\system32\lsass.exe (file missing)
O23 - Service: NVIDIA Performance Driver Service - Unknown owner - C:\Program Files\NVIDIA Corporation\Performance Drivers\nvPDsvc.exe
O23 - Service: NVIDIA Display Driver Service (nvsvc) - Unknown owner - C:\Windows\system32\nvvsvc.exe (file missing)
O23 - Service: @%systemroot%\system32\psbase.dll,-300 (ProtectedStorage) - Unknown owner - C:\Windows\system32\lsass.exe (file missing)
O23 - Service: @%systemroot%\system32\Locator.exe,-2 (RpcLocator) - Unknown owner - C:\Windows\system32\locator.exe (file missing)
O23 - Service: @%SystemRoot%\system32\samsrv.dll,-1 (SamSs) - Unknown owner - C:\Windows\system32\lsass.exe (file missing)
O23 - Service: @%SystemRoot%\system32\snmptrap.exe,-3 (SNMPTRAP) - Unknown owner - C:\Windows\System32\snmptrap.exe (file missing)
O23 - Service: @%systemroot%\system32\spoolsv.exe,-1 (Spooler) - Unknown owner - C:\Windows\System32\spoolsv.exe (file missing)
O23 - Service: @%SystemRoot%\system32\sppsvc.exe,-101 (sppsvc) - Unknown owner - C:\Windows\system32\sppsvc.exe (file missing)
O23 - Service: TeamViewer 5 (TeamViewer5) - TeamViewer GmbH - C:\Program Files (x86)\TeamViewer\Version5\TeamViewer_Service.exe
O23 - Service: @%SystemRoot%\system32\ui0detect.exe,-101 (UI0Detect) - Unknown owner - C:\Windows\system32\UI0Detect.exe (file missing)
O23 - Service: @%SystemRoot%\system32\vaultsvc.dll,-1003 (VaultSvc) - Unknown owner - C:\Windows\system32\lsass.exe (file missing)
O23 - Service: @%SystemRoot%\system32\vds.exe,-100 (vds) - Unknown owner - C:\Windows\System32\vds.exe (file missing)
O23 - Service: @%systemroot%\system32\vssvc.exe,-102 (VSS) - Unknown owner - C:\Windows\system32\vssvc.exe (file missing)
O23 - Service: @%systemroot%\system32\wbengine.exe,-104 (wbengine) - Unknown owner - C:\Windows\system32\wbengine.exe (file missing)
O23 - Service: @%Systemroot%\system32\wbem\wmiapsrv.exe,-110 (wmiApSrv) - Unknown owner - C:\Windows\system32\wbem\WmiApSrv.exe (file missing)
O23 - Service: @%PROGRAMFILES%\Windows Media Player\wmpnetwk.exe,-101 (WMPNetworkSvc) - Unknown owner - C:\Program Files (x86)\Windows Media Player\wmpnetwk.exe (file missing)