It's really strange situation that i cant't figure out.
Motherboard: ASRock G41M-GS3, Inter Core 2 DUO 2.13GHz, new PSU (Xilence 480W). Problems start when i try to put in it my Radeon HD3850 - PC starts and shuts down in couple of seconds (POST does not complete). The interval between startup and shutdown is random, sometimes its less than second, sometimes 4-5. If i didn't power off the supply, it keeps trying to power up endlessly.
If i put the card in another computer, it works fine. If i put low-end video card (GeForce EN7300GS) in that new PC, it also power-ups fine.
I tried to power up only with video card (without HDD and optical drives), no change.