I ran into an interesting issue the other day. A machine registered in WSUS would appear and then dissapear from the WSUS 3 SP1 console.
Found the solution to the problem on the following links:
http://tinyurl.com/mrxrwt – best source
Here is a script that will run only once if completed successfully. It will also write a log in either case to a subfolder where it ran from with a computer name in the file name.