Program stops responding and alt+ctrl+del stops working

I recently started getting very annoying problem. Firefox or other program stops responding and alt+ctrl+del stops working at the same time so I have to reboot. It happens quite often.

What I did already:
*Maybe virus? Full boot time system scan with Avast anti-virus. Nothing found.
*Oh well reinstall windows again... Yes, I did that too. Still same problem BUT ONLY after small break like two days or so.
And most confusing thing is that full screen programs like games do not seem to stop responding. Still, they BSOD like after few hours, but I do not think it is related. Like heavy load or something.

My system details hopefully in my forum profile, at least filled them recently.

So any other ideas how I can fix that?

Maybe I will post my BSOD problems separately, besides they are no so bad. Main really bad problem is that programs stop responding together and alt+ctrl+del stops working at the same time. It happens like after 5 minutes of windows use.

I have no overclock at all. Never did that.

I already moved to exactly Panda together with windows reinstall, but still never did full scan with it yet. I will try that. Maybe virus still lingering in my data drives...

I will try to off gpu acceleration in browser.
I remember really well that Avast crashed during quick scan. I will provide other crashing programs as they will crash. Currently, after reinstall, I have very few just stock windows programs, panda, firefox, nvida drivers and few games I decided to leave with my data.

I tired Panda "Critical are scan". It stopped responding multiple times. In most cases on 1% without even showing exact file, once I recorded file "cmncliM.dll".
Removed nvida stuff completely still same.
Moved to safe mode everything was better there still no luck with Panda scans. So removed Panda too.
Interesting that problem seems gone now..., but no antivirus heh.
And same was with Panda and with Avast.
So I got Kaspersky 30 days trial now. Did quick scan nothing found.
Still doing full system scan. But it is kinda fixed now.
Going to reinstall nvida later. Hopefully it will be OK with it too.
Also do not know what I will do after Kaspersky trial end, still not going to pay hehe.
Thanks to all who posted to help, and still feel free to post you free anti-virus recommendations.

Well, after Panda replacement with Kaspersky problem was completely gone.
Now I plan to move to Bitdefender in the end of Kaspersky trial.