Not long after upgrading to VS2010, my application won't shut down cleanly. If I close the app and then hit pause in the IDE, I see this:

The problem is, there's no context. The call stack just says [External code], which isn't too helpful.

Here's what I've done so far to try to narrow down the problem:

• deleted all extraneous plugins to minimize the number of worker threads launched
• set breakpoints in my code anywhere I create worker threads (and delegates + BeginInvoke, since I think they are labeled "Worker Thread" in the debugger anyway). None were hit.
• set IsBackground = true for all threads

While I could do the next brute force step, which is to roll my code back to a point where this didn't happen and then look over all of the change logs, this isn't terribly efficient. Can anyone recommend a better way to figure this out, given the notable lack of information presented by the debugger?

The only other things I can think of include:

• read up on WinDbg and try to use it to stop anytime a thread is started. At least, I thought that was possible... :)
• comment out huge blocks of code until the app closes properly, then start uncommenting until it doesn't.

UPDATE

Perhaps this information will be of use. I decided to use WinDbg and attach to my application. I then closed it, and switched to thread 0 and dumped the stack contents. Here's what I have:

ThreadCount:      6
UnstartedThread:  0
BackgroundThread: 1
PendingThread:    0
DeadThread:       4
Hosted Runtime:   no
                                   PreEmptive   GC Alloc                Lock
       ID  OSID ThreadOBJ    State GC           Context       Domain   Count APT Exception
   0    1  1c70 005a65c8      6020 Enabled  02dac6e0:02dad7f8 005a03c0     0 STA
   2    2  1b20 005b1980      b220 Enabled  00000000:00000000 005a03c0     0 MTA (Finalizer)
XXXX    3       08504048     19820 Enabled  00000000:00000000 005a03c0     0 Ukn
XXXX    4       08504540     19820 Enabled  00000000:00000000 005a03c0     0 Ukn
XXXX    5       08516a90     19820 Enabled  00000000:00000000 005a03c0     0 Ukn
XXXX    6       08517260     19820 Enabled  00000000:00000000 005a03c0     0 Ukn
0:008> ~0s
eax=c0674960 ebx=00000000 ecx=00000000 edx=00000000 esi=0040f320 edi=005a65c8
eip=76c37e47 esp=0040f23c ebp=0040f258 iopl=0         nv up ei pl nz na po nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00000202
USER32!NtUserGetMessage+0x15:
76c37e47 83c404          add     esp,4
0:000> !clrstack
OS Thread Id: 0x1c70 (0)
Child SP IP       Call Site
0040f274 76c37e47 [InlinedCallFrame: 0040f274] 
0040f270 6baa8976 DomainBoundILStubClass.IL_STUB_PInvoke(System.Windows.Interop.MSG ByRef, System.Runtime.InteropServices.HandleRef, Int32, Int32)*** WARNING: Unable to verify checksum for C:\Windows\assembly\NativeImages_v4.0.30319_32\WindowsBase\d17606e813f01376bd0def23726ecc62\WindowsBase.ni.dll

0040f274 6ba924c5 [InlinedCallFrame: 0040f274] MS.Win32.UnsafeNativeMethods.IntGetMessageW(System.Windows.Interop.MSG ByRef, System.Runtime.InteropServices.HandleRef, Int32, Int32)
0040f2c4 6ba924c5 MS.Win32.UnsafeNativeMethods.GetMessageW(System.Windows.Interop.MSG ByRef, System.Runtime.InteropServices.HandleRef, Int32, Int32)
0040f2dc 6ba8e5f8 System.Windows.Threading.Dispatcher.GetMessage(System.Windows.Interop.MSG ByRef, IntPtr, Int32, Int32)
0040f318 6ba8d579 System.Windows.Threading.Dispatcher.PushFrameImpl(System.Windows.Threading.DispatcherFrame)
0040f368 6ba8d2a1 System.Windows.Threading.Dispatcher.PushFrame(System.Windows.Threading.DispatcherFrame)
0040f374 6ba7fba0 System.Windows.Threading.Dispatcher.Run()
0040f380 62e6ccbb System.Windows.Application.RunDispatcher(System.Object)*** WARNING: Unable to verify checksum for C:\Windows\assembly\NativeImages_v4.0.30319_32\PresentationFramewo#\7f91eecda3ff7ce478146b6458580c98\PresentationFramework.ni.dll

0040f38c 62e6c8ff System.Windows.Application.RunInternal(System.Windows.Window)
0040f3b0 62e6c682 System.Windows.Application.Run(System.Windows.Window)
0040f3c0 62e6c30b System.Windows.Application.Run()
0040f3cc 001f00bc MyApplication.App.Main() [C:\code\trunk\MyApplication\obj\Debug\GeneratedInternalTypeHelper.g.cs @ 24]
0040f608 66c421db [GCFrame: 0040f608]

EDIT -- not sure if this helps, but the main thread's call stack looks like this:

    [Managed to Native Transition]  
>   WindowsBase.dll!MS.Win32.UnsafeNativeMethods.GetMessageW(ref System.Windows.Interop.MSG msg, System.Runtime.InteropServices.HandleRef hWnd, int uMsgFilterMin, int uMsgFilterMax) + 0x15 bytes  
    WindowsBase.dll!System.Windows.Threading.Dispatcher.GetMessage(ref System.Windows.Interop.MSG msg, System.IntPtr hwnd, int minMessage, int maxMessage) + 0x48 bytes 
    WindowsBase.dll!System.Windows.Threading.Dispatcher.PushFrameImpl(System.Windows.Threading.DispatcherFrame frame = {System.Windows.Threading.DispatcherFrame}) + 0x85 bytes 
    WindowsBase.dll!System.Windows.Threading.Dispatcher.PushFrame(System.Windows.Threading.DispatcherFrame frame) + 0x49 bytes  
    WindowsBase.dll!System.Windows.Threading.Dispatcher.Run() + 0x4c bytes  
    PresentationFramework.dll!System.Windows.Application.RunDispatcher(object ignore) + 0x17 bytes  
    PresentationFramework.dll!System.Windows.Application.RunInternal(System.Windows.Window window) + 0x6f bytes 
    PresentationFramework.dll!System.Windows.Application.Run(System.Windows.Window window) + 0x26 bytes 
    PresentationFramework.dll!System.Windows.Application.Run() + 0x1b bytes 

I did a search on it and found some posts related to WPF GUIs hanging, and maybe that'll give me some more clues.