Is AVG up to date? is adware up to date? also try using a second spyware/malware scanning program such as spybot search and destroy or Windows Defender from Microsoft.
Like was said before me, boot into safe mode. Thats the best place to scan for spyware/ viruses.
try that and if that dosent work , attempt a windows repair.
P.M. me on how to do a windows repair.