Bummer , I would suggest installing windows sp3 from here :
http://www.microsoft.com/downloads/d...displaylang=en
Youll probably have to disable your firewall to do this.
Make sure all your windows components are up to date too by checking for updates.Then try un-installing and re-installing both browsers if that doesnt work , deleting any entries relating to them in program files.
It could possibly be a virus , you could uninstall AVG and install Avast! free edition instead , its a much better program in my eyes.
If you dont want to do that I suggest turning system restore off , then scan again using AVG.
Let me know how you get on.