All games hang/Freeze in Win7 x64, on nvidia GTX260

Hi all,
I was really hoping to avoid having to post here and bug you all, but my hours of googling have turned up basically nil.
Here's the short run-down, more details available upon request.
My rig is built by me, and spec'd as follows:
CPU: Q9450 @ stock clocks w/ aftermarket tower cooler (runs stone cold) (Original CPU of the same model died and was replaced by intel, no change in issue)
Mobo: eVGA 780i SLI (replaced due to thinking it was the cause of the CPU issue, oops!)
Mobo Bios: 2.053.L4 (Apparently P10 is the latest, but only adds CPU compatibility?)
PSU: Tagan BZ 900W modular (tested good with external PSU tester)
RAM: 6GB Corsair Dominator DDR2-8500C5D @ 1066Mhz and recommended timings and voltages (checked error-free with memtest 86+)
HDD: WD Velociraptor 300GB (OS Drive), Seagate 1TB (storage and games drive)
GPU: GTX260 216, bios 62.00.4c.00.02 (Core Clock: 720, shader clock: 1552, mem clock: 1100 all per Precision) <-GPU OC is NOT the source of the problem
GPU Driver: 257.21 WHQL
Dual monitors: (1) Acer 24" @ 1920x1200, (2) Dell 20" @ 1600x1200
OS: Win7 x64 Ultimate, all updates/patches as of today (7-5-10)
Have I missed anything important?

Anyway, here's the issue:
Since upgrading to Win7 x64 several months ago, I've noticed that all my games periodically freeze up during play. Sometimes it happens in a couple minutes, other times I can play long enough to forget about it until it returns and really pisses me off! >
- I've tried multiple drivers, both stock and custom, from the first win7 betas up to the current version.
- I've tried doing in-place driver upgrades, as well as clean sweeps with new drivers from scratch.
- I thought my GPU Overclock was causing the hangs, so I pulled it back to stock, no change.
- I suspected my GPU itself could be failing, so I swapped it out with my old card (8800GTS G92) and it exhibited the exact same symptoms.
- I had a bad stick of RAM at one point, so I RMA'd the pair to corsair and they replaced them. No change.
- I suspected GPU overheating may be the issue, so I loaded up Precision and Furmark and let 'er rip. The card idles around 55c. I think Furmark got it up to maybe 85c. By then, the fan had spooled up to around 60% (I think) and the thermals stabilized. However, about 3-4 minutes into the run, Furmark hangs, and windows pops up the "video driver has stopped responding and has been successfully recovered" message. So the issue occurs in both 3D games and synthetic testing.
Here's the weird thing: I can boot back into Windows XP Pro (dual booting FTW!) and everything runs smooth, no freezes, no hangups.
Here's the even weirder thing: When the game hangs, I can Ctrl-Alt-Del to get to the welcome screen, then hit Esc and the game (usually) unlocks and I can continue playing. In some games, I'm back to the welcome screen every 10-12 seconds, other times every couple minutes. Eventually, I either get frustrated and quite out of the game or it finally locks hard enough to crash to desktop with the "xxxx has stopped working" message.

I've tested or replaced almost every single piece of hardware in this rig, with the exception of the HDDs and Optical drives.
I'm about out of ideas, can anyone help?
Where should I go from here?
Any advice appreciated.

PS: I've linked to the full sysinfo log from the nvidia control panel, in case anyone wants to know way too much about the internals of my hardware.

Hi.

It's generally known to be a little impolite to post across multiple forums the same exact request for help. Just saying...

http://windows7forums.com/windows-7-...ia-gtx260.html