I believe that's what they refer to as a retro virus. In this case it sounds like a hybrid of a trojan and retro virus. Retro viruses are ones that seek the security software and usually delete the virus definition file so they can't be detected. Trojans are programs pretending to be something else. In this case, I would recommend re-installing your anti-virus and running a full blown scan. Then uninstall and install free trials from Macaffe and Trend Micro. (A bit overkill, but I don't play around when I know I got a virus that is getting around my antivirus) If it prevails against all three, reformat your pc is the only option left.
One tip though. Never use the online scans, even from reputable companies...If you do have a virus, it always locks up the scan and freezes up your pc. Or that's been my experience anyways.