Random restarts while gaming

so i'm going to get right into it. i recently upgraded my video card to an 8800gt and installed a new watercooling loop. my q6600 at 3.0ghz idles at 28 for cores 1 and 2, and 32 for cores 0 and 3. at full load, they are all round 45. at 3.6ghz, the temps are only a couple of degrees higher. temps were taken using both coretemp and speedfan. this is cooled using an alphacool nexxxos xp block. my 8800gt reports an idle temp of 35 degrees, and after about an hour of playing ghost recon advanced warfighter 2 with all eye candy enabled, it was only at 38, peaking at 39 for a bit. this was taken using rivatuner. the gpu has a d-tek unisink and a swiftech mcw-60r waterblock.

well as of today, after about 20 minutes of gaming it just randomly shuts off. i tried setting my bios back to factory default. my video card has not been overclocked yet so it's still running the stock frequencies. i also made sure that there was proper contact between the waterblocks and cpu/gpu.

my power supply is an antec neohe 550 and i also have a thermaltake 250w vga power supply just for the video card.

my specs: q6600 at 3.6ghz, 2gb of crucial ballistix tracer ram, dfi p965-s dark motherboard, 8800gt, creative x-fi sound card, nec sata dvd burner, raptor 74gb main drive, two 300gb storage drives.

when benchmarking or stress testing, the computer runs fine.

any help would be greatly appreciated.

i'll give it a shot. i've been using that thermaltake supply for a long time (used it with my 7950gx2 and my 2900xt) and i never had this problem, but i'll give it a shot when i get home from work.

try to increase the voltage of the cpu
at higher clock speeds, processors require more voltage so that they do not make any errors
do prime95 benchmark for your overclocked cpu
windows restart the pc when it encounters massive errors

geofelt...my temps are actually better now that i went to half inch i.d. (used to be 3/8 inch. my video card drivers are the most recent from nvidia's website. i'm eventually going to get 4gb of ram, but i still can't afford it right now. lastly, my sound card drivers are the same as they were when i had the 2900xt and i had no problems like that before the gpu upgrade.

i'm currently reinstalling windows, so we'll see what happens

The only times I had these issues:

1). Bad power supply.

2). ATX connector melted to motherboard after spilling milk down my fan port...oops, but I doubt thats the prob u have.

3). Bad timings set on the RAM.


Other suggestions:
1). Research nVidia forums for the same issues.

2). Make sure your vid card doesn't have a factory OC on it as it may be causing issues with your system.