In a recent Facebook discussion about whether or not a problem with Media Center was caused by a virus or just some goofyness with the computer, I had this to say:
"I've heard people tell others that stupid Outlook behavior was caused by a virus… when it was just stupid Outlook behavior so I tend to not to blame every thing on viruses. Unless you want to refer to users as viruses." — Diane Poremsky August 27 2011
The user said Norton came up clean. It's the suite that does everything and my suspicion is that it munged the registry and caused the problems.