My eternal thanks for the guru who knows what on earth is happening with my home-built machine.
I'm running Vista 64 with an XFX board and an Nvidia GTX 280 card. I don't have a separate audio card, and I've updated with the latest NVIDIA video drivers and RealTek audio drivers from XFX.
The problem is that I'm experiencing complete system freezes (such that it forces a hard reset), often when playing audio or video (although I'm not sure if that's coincidental, as once or twice it has frozen without audio or video playback). Occasionally just before the freeze happens, the video playback (usually web video) will begin to experience odd "fuzziness," as you might see on an old analog TV with bad reception.
When the audio freezes, it locks at a specific point in playback and will "skip" in that pattern indefinitely. This is usually while running iTunes, although it happens with any audio, be it from YouTube, Hulu, WMP, etc. Rarely, the lock-up will only be for 1-2 minutes, whereupon it will resume playback and the system will un-freeze. Usually the system will freeze up again after several minutes, though.
The final oddity to all this is that if I just press the "reset" button on my case, often the system won't fully restart: it will either stay at the "XFX" logo screen indefinitely, or else when the Vista "load bar" begins scrolling across the screen, it will lock up and never recover. In order to successfully reboot, I have to press the hard reset button; and then while it's booting, press the hard power switch to completely power down. I'll then wait a minute or two, press the power button again, and (usually after a few tries of this) it will successfully boot.
I'm running at 2560x1600 on a 30" Dell 3000WFP monitor. Occasionally after I've finally successfully rebooted, the screen image will be corrupted/pixelated as if the monitor is trying to stretch a smaller image onto the screen without interpolating. In order to fix this pixelation, I have to switch the screen resolution to 1920x1200 (which stops the pixelation); and then go into the NVIDIA Control Panel and reset my resolution to 2560x1600. Then the image appears normal again.
I'm a bit at my wit's end here: again, I've loaded up the most recent NVIDIA drivers for my card, and the latest RealTek audio drivers, as for a while I thought that might be contributing to the problem. Neither has seemed to solve anything.
I'd appreciate any ideas on how to solve this, because short of flashing a new BIOS (which I can't imagine would be related, but stranger things have happened), I'm really at a loss as to what's happening here.
Just to conclude this posting: I think I may have resolved the issue. The one thing I hadn't taken into account was heat; although I had never had a heat problem before (this machine was built approximately 10 months ago), I decided to take a shot at it and removed one of the side panels. I then let it run like that for several days.
I haven't had so much as a hiccup since then.
Let this be a lesson to everyone: sometimes the most insurmountable problems turn out to be the easiest to solve! I'll cross my fingers that this is indeed a fix.