May I suggest you try the following:
FIRST: Go to Adminstrative Tools>Disk Cleanup>Cleanup System Files (if a big update is stuck it will take awhile to think)>make sure the Windows Update Cleanup, Temporary Internet Files and Temporary Files boxes are checked>Now Run the Cleanup
NEXT: Go to Administrative Tools>Services>Windows Installer>Start then Stop the service
Now down a little further on the list find Windows Update>Start then Stop the service
REBOOT YOUR COMPUTER GO TO WINDOWS UPDATE AND TRY AGAIN
Although I don't have your problem I think this may fix it. Hope it works!
Lee