This is kind of a long post, because this is a fairly weird problem. I'll explain.
I assembled a computer about 2 years ago. The hardware was
CPU: Intel Core i7 2600K 3.4G 8M
Mobo: MSI P67A-G43 (B3) P67 LGA1155 Motherboard
Video: Gigabyte GV-N56GOC-1GI GTX560
PSU: Corsair 750W CMPSU-750TXV2
RAM 4Gx2 GSKILL F3-10666CL9D-8GBRL
HDs: 2 x 2T Seagate Barracuda SATAIII ST32000641AS
Optical drives: LG GH22NS50 dvd burner and
Samsung BD combo drive SH-B123L
I had a Dell keyboard and a Logitech mouse. Nothing fancy. OS is Windows 7 64-bit (Enterprise, SP1).
Everything was A-ok with the system until a few months ago. The computer began to periodically turn off my monitors for no reason, usually when I clicked the mouse. That is, I never observed it happening in the middle of a video playing, or when the computer was idle, when I wasn't interacting with the computer---only when I was actively moving windows around or such. For awhile, I found that pulling out the USB cable of the mouse and plugging it back into another port would get the monitors to turn back on, and the computer could be used again, though the problem would still recur eventually. The system would be fine for hours, days, even weeks at a time, and then a rash of such events would happen.
A month or so ago, though, the problem became more acute. The system was not only shutting off the monitors, but really freezing the system (seemingly ... it's hard to tell when the monitors won't turn on). Only pressing the reset button or powering off would get it back. Moreover, I started getting errors on my main drive after these freezes, which were always fixable by Checkdisk upon reboot. And the problem was happening every few minutes, not hours.
Since the issue appeared to be USB related (correlated with clicking), the first thing I swapped out was both my keyboard and mouse for a set I had lying around, but that had no effect, nor did any combination of USB ports, either on my case's front panel or in the MB directly. Because I was getting HD corruption, my next two suspects were the motherboard and hard disk. So, I bought a new mobo (never liked that MSI board anyway) and a new hard drive (SSD). Updated hardware:
HD: Samsung 840 Pro Series MZ-7PD256BW 2.5" 256GB SATA III
Mobo: Gigabyte GA-Z77MX-D3H LGA 1155
And things were better for a time. I had no real issues for the first few days after reinstalling Win7 and all my programs. Then the computer began to freeze, again usually correlated with clicking on something. The new SSD drive got corrupt sectors or orphaned files on these freezes, same as the platter HD did, and they are always reparable.
Now it's happening quite frequently. Interestingly, though, the monitors do not turn off now when the freezing happens; the computer usually just locks up or cannot be interacted with. Pulling the USB peripherals out has no effect. Other times, the mouse cursor turns invisible---I know it is moving around because elements on the screen are highlighting, but the cursor itself stays frozen to where it was when the problem happened. Sometimes I can even get my invisible cursor down to the Start Menu to tell it to restart, though it never does that successfully.
The last ditch effort I made was to unplug the front panel USB ports from the motherboard, but that had no effect. I do still have the 2 2TB drives from my previous setup installed as secondary drives, but they stay powered down most of the time, and I don't think (though I cannot prove it) that they are involved. I also do not think it is software related, though again I can't really prove it. However, I can get the problem to happen after Windows boots by launching only Firefox and playing around with it for a few minutes, with no other programs running except background stuff like Dropbox. Thus, I think this is a hardware problem. Because the mobo and HD are new, I would think it has to be the video card, RAM, CPU, or PSU.
The issue started with monitors turning off, so my next culprit would be the video card. What do people think? I suppose I don't mind dropping a few hundred on a new card, since mine is getting a bit old, but on the other hand the card may be just fine (as, indeed, I now think the original motherboard was).
If you read all the way to the end of this, thanks. I'd appreciate any suggestions people have. I'm not exactly a n00b, but this has me puzzled.