Don't be so quick to judge freeware AV programs... In alot of cases they DO outperform paid for varieties.
Quote: "i fully scanned my PC with AVG and Symantec online scan. no threads were found"
Norton AV is actually a Symantec product, so if an online scan didn't detect anything (the online scans have the most up to date virus definitions), I very much doubt Norton would have detected it too.
As TheNerd said, this might actually be a new piece of malware which there are no definitions for yet.
A couple of quick questions, what operating system are you running? have you downloaded anything online that might have caused this? (P2P file sharing maybe), have you installed anything immediately prior to the problem(s)? and if so what? was there anything that might have been changed before the problem(s) occurred that might have contributed (software installation)?
If you can provide as much info as possible it would be helpful. There are some malware out there that create random .dll files, virtumomde and Vundo do this, so the more info you give us the better armed we are to help.