Windows SP2 Firewall keeps turning off

It could be a virus, although I have scanned many times with norton 04, avg, spyware s+d, online McAfee…

Any ideas why the firewall keeps turning off? (I activate it, turn off, back on later and the FW is off again.)

Thanks.

Seems strange. I don’t use the Windows firewall myself since the ones like Agnitum and Sygate seem to be better and free.