Something very nasty nailed me yesterday right after I booted my WIN 7 x64, Comodo 5.x.x.1355, MBAM Pro, Avast 6.x installation.
A couple minutes after my Avast def. update completed, my daily scheduled Avast quick AV scan started. Shortly therafter it hung. WTF! This never happened before. Tried get to Task Manger via Ctl-Alt-Del, no go. Had to do a cold power button shutdown.
Rebooted a couple of times only to find I can not access any of my anti-malware scanners. Every attempt hung the PC. Booted into safe mode. Anti-malware scanners worked there but didn’t find anything. Finally booted off my Avast Recue CD and it found Win32:FakeVimes-B [Trj] in pagefile.sys. That was interesting since it was the same Trojan that Avast’s normal mode memory scanner found associated with Comodo’s cmdagent.exe. The Avast forum people told me that this was a FP due to being an unencyrpted virus signature.
Deleted pagefile.sys and rebooted. PC still hosed. Gave up and restored from a week old image backup and all is fine. Comodo back at firewall only versus proactive and I am keeping it that way. No clue what nailed me but it was bad news!