After I reinstalled Windows 7, Disk Cleanup stopped working.
I can start Disk Cleanup and select the drive to clean, but when I click on the OK button, the window disappears.

Any solutions?

Here's the data from Windows Logs>Application :-

EventData
1744235005
1
APPCRASH
Not available
0
cleanmgr.exe
6.1.7600.16385
4a5bc5e1
Csi.dll
14.0.4733.1000
4b5662be
c0000005
00135213

F:\Users\Jacob\AppData\Local\Temp\WER419.tmp.WERInternalMetadata.xml
F:\Users\Jacob\AppData\Local\Microsoft\Windows\WER\ReportArchive\AppCrash_cleanmgr.exe_6514b6ecb633f97cbf78e3a5bcae2c4bd74351_0d3b109c
0
75fa9599-41b1-11e0-b864-001966b2bcb6
0

The above one was with an Information icon.

The one below was with an Error icon:--

EventData

cleanmgr.exe
6.1.7600.16385
4a5bc5e1
Csi.dll
14.0.4733.1000
4b5662be
c0000005
00135213
bbc
01cbd5be36b572bf
F:\Windows\system32\cleanmgr.exe
F:\Program Files\Common Files\Microsoft Shared\OFFICE14\Csi.dll
75fa9599-41b1-11e0-b864-001966b2bcb6

I also used process explorer:-
When i started disk cleanup, a cleanmgr.exe process appeared under explorer.exe.But when i clicked on the "OK" button after selecting the drive, cleanmgr.exe was there for some seconds before it disappeared. But a new process - WerFault.exe appeared under svchost.exe a few seconds after i clicked the "OK" button. It disappeared, too, from the process list after some time (i think it disappeared along with cleanmgr.exe).