I haven't got the details in front of me, but I understand MS is sending out a patch of a patch. It sounds like a fairly common thing that some computers got broken by recent update. Again, I didn't pay attention to the symptoms so I don't know if this is the same problem described here.

Edit:

Here is a quick link that I found. The problem I was remembering sounds similar to yours:

PCWorld article 

and 

Microsoft blog discussion