WSUS hangs on Cleanup wizard for Unused Updates, then disconnects from console.

I am running WSUS 3.0 SP1 on Windows 2003 and recently have found that running the Cleanup Wizard works with all of the selectable options except the "Unused Updates" option. It hangs about 1\2 way through and then disconnects from the console. Up until now it has worked.
I am using the Windows Internal Database and the size of the MDF is 3193024kb.
Everything other than this wizard is working fine. Please help.