did you turn on heuristics in Antivir?
and what detection level is it on?
personally I haven't encountered a virus Antivir has missed, although no antivirus program is perfect.
you might be one of the first people with that particular virus
you might want to try AVG (also free), or if you can, try manually deleting it by going into safe mode, looking in the \Windows and \windows\system32 folders, arranging by date, and finding any .exe's or suspicious files without an author. at the end