Nvidia 9600GT SLI Problem Please Help

Hello anyone who reads this. I'll get straight to the point.
I have recently built a new desktop computer with the following specs:

Case:COOLER MASTER Stacker 810
PSU:Rosewill RX750-S-B 750W 80Plus Certified
CPU:Intel Core 2 Quad Q6600 Kentsfield 2.4GHz
MEMORY:G.SKILL 2GB 240-Pin DDR2 SDRAM DDR2 800
MB:EVGA 132-YW-E178-A1 LGA 775 NVIDIA nForce 780i SLI FTW
GPU:BFG NVIDIA GeForce 9600 GT OC 512MB PCIe 2.0: (x2)
OS: Vista 64bit

I am new to the concept of SLI. The problem that I keep running into is when I try to play games. Mainly I play CS:Source. I would be playing for about 30minutes and then the screen goes blank and the sound gets choked up and repeats until the screen goes to my desktop.In some rare occasions the blue screen of death would show up and I end up restarting. But other than that once the game shuts down I get an error msg about an APPCRASH. I would also get the same thing for COD4. I have read many forums and have taken their advice by.

So far I have tried:
1. Reinstalling Vista
2.Reinstalling the Games
3.Updating to the newest drivers for MB(nForce v.15.23 WHQL) and GPU(GeForce v181.20)
4.Checking if both GPUs were working
5.Used RivaTuner to turn up GPU fan speed for possible overheating (during idle stays at 50c and during its peak it reaches high 60c)


**Here is the weirdest thing. When I do not enable SLI mode and run a game on 1 GPU it does not freeze. But after I am done playing I still do get the occassional APPCRASH error.

Please if anyone could help me find what the problem might be when trying to run SLI for my computer games?

The problem may lie with Vista 64, if you can give Vista 32 a go.

The problem could be with your power supply. SLI needs a minimum of 450w, 12v, 28Amp to run properly.