Ati 4870 installed - random shut down

I recently bought an ATI 4870 and I works great, except...this morning my computer just shut down with no reason. I wasn't gaming and all my temps were within the specs (highest CPU core temp 42 C - monitored with SpeedFan and RealTemp - the difference is 2 degrees; card temp - idle - 43 C, under load 56 - fan speed set to 45%). The power supply is an OCZ StealthXtream 600W and is ATI certified. When I tried to turn on the computer the monitor wouldn't turn on. So I shut down the power supply and tried to start it. At first it tried to power on but shut down again and tried to start again on its own. It did this 2 times and then correctly started. Do you think its something wrong with the card, or the power supply? (Sorry if this is the wrong forum)

If it were the power supply dont you think I would have shut down during gameplay? I played Crysis , UT3, Devil May Cry 4 for hours with no incident whatsoever. The computer shut down when idle...

oooo weird problem! just lupi's type of thing

I checked, but forgot to mention in the original post. The only thing it says is that there was an unexpected shutdown.

Perhaps I should reinstall my chipset drivers too then!
Since upgrading to the sapphire 4870 my raid 1 system has had frequent ntfs errors (jmicron chip), and gigabyte tells me that everything in my system should work just fine together,and i should check my harddrives for errors. They're fine, but the system keeps creating filesystem errors after upgrading .....

ps. ocz is fine - it's not top notch, but their stuff usually works. First time I bought something from them was back in 2001 when they supplied voltmodded abit motherboards with unlocked thunderbirds ....

It could be your memory, I had this promblem where It shut down and didn't reboot till I removed some of my memory and it booted again. It could be your PSU since it is sorta old.

The Q6600 Processor was my problem "random shut downs" normally after 2-3 days. I replaced 2 hard drives, 1 power supply, 2 mother boards, 2 graphic cards, and one case (thought it was grounding out). It took me over 15 months to figure this out. It seems the 1% (NewEgg comments) of those who do not love this processor experienced the exact same problems. Always the last part before you torch your entire system and the least likely. Intel is in the process of replacing it, but talk about a great deal of time and money to figure it out.