What is going on with my computer visually

OK..

Last week I am playing an mmo, and my computer flashes gets a "nvidia driver problem... corrected itself" twice in about 2 min.

Then the computer screen went black and when powered back on. nothing shows up.

After a bit, visually comes on then dies.

I look in event viewer and notice some problems with a driver from my network K1 card so I go and get new drivers for it and my vid card just to be safe.

Problem happens again. I try moving monitor to connected to my second GPU to see if its just one. I did not think I had them running SLI so figured it would work. No response.

AFter a bit, starts working fine again.

Next day. again. This time i remove one video card that i suspect might have a problem. No problems.

Then today i power up my computer and the power goes on but nothing visually. After about 20 seconds i hear a beep. after about 1 minute, the computer comes on and goes through normal startup cycle.

No clue if this is a gpu, motherboard, or a possible power supply problem

my computer:

500 GB SATA II 3.0 GB 16MB 7200RPM
4x 1G DDR2 PC6400 MEMORY
BLACK SONY 1.44MB FLOPPY DRIVE
KILLER K1 HIGH SPEED NETWORK CARD
2x EVGA NVIDIA 9800GTX+ 512MB PCI-E
BLACK SAMSUNG 20X DVDRW
BLACK 16X DVD ROM
ASUS 780SLI P5N-T DELUXE MB
NZXT 800 WATT POWER SUPPLY SLI
INTEL QUAD CORE Q9550
THERMALTAKE V1 GAMING CPU FAN
windows 7 64 bit

I should also note that I have been monitoring the temp and all cores before and after, and during running are all under 45 degrees and gpu cards never get above 63 degrees (rated for over 100)