Microsoft update error pop-up

Hello!
Not on this computer, but on a laptop using MS Vista Home Basic, I am getting a pop-up saying that "Microsoft cannot update - click here to fix". This has been popping up every few hours for 3 weeks or so.

Checking the update log, the auto-update is "ON" and working perfectly (there are 30 - 40 updates downloaded and installed since the pop-up appeared first).

Is this a known scam, or some other error?

Thanks in advance,
Chris

We'll find out here...

We Need to Diagnose a Possible Problem with WGA
This may be preventing you from installing updates.

1. Please download MGADiag and save it to your desktop.
   
2. Double click the icon on your desktop.
   
3. Push
   
4. Push
   
5. Go to Start -> Run and type in "Notepad"
   
6. Go to Edit -> Paste in notepad.
   
7. Copy and paste that log here.

Hi.

Thanks for your suggestion - somehow I lost the thread.

The error 'solved itself' the day after I asked for your help - must be your influence!  

Thanks again for being there to help.

best, Chris