Interesting article on the Lockergnome blogs:.
It would appear that AVG was showing false positive results for genuine Windows files. I experienced that too with both Windows files and WinAmp Pro, which after one AVG update told me was a virus or trojan.
Worryingly, after I moved to Symantec Norton Anti Virus 2009 it identified a couple of files as containing trojans, that I know I scanned with AVG after downloading and AVG falsely informed me were clean.
So far, I’m having a good experience with Norton Anti Virus 2009. Good work Team Symantec!