Monitor issues

Hi,

I have two monitors, both plugged into my GTX650Ti graphics card, one HDMI and the other VGA. This setup has been working fine for months.
Yesterday, when I woke up, only my second monitor (VGA) was working, and the resolution had been reset to 800x600. I logged in, and it looked like the computer had reset itself during the night. I could not get the PC to detect the second monitor, even though it is on, and actively searching for inputs.
Thinking it might be the cable, I bought a new one. When I unplugged the old cable, the monitor flashed a warning (Check Video Cable). I plugged the new cable in, and again the monitor began searching for inputs, to no avail.
One windows update was installed that night, which caused the reset of the computer. I have uninstalled that update, but it hasn't solved the problem. I tried again to detect the new monitor (clicked detect on the screen setup page), and my antivirus popped up and said ATI.exe virus had been detected and it deleted the file.
Could a virus cause this problem?
I have installed all the latest drivers, and this has not solved the problem.

Any ideas?