Radeon 4850?

Does anyone know what the minimum amperage that's required to run this card? My PSU has 24 A on the +12 V rail and 550 W max overall

well, here's my problem

The computer will turn on and the fans and everything sounds normal when there is no connector bringing power to the graphics card....

However, when I plugged in the graphics card power and tried to turn the computer on, it turned on for about half a second and then everything shuts off.....and then I let it sit for a while and unplugged the graphics card power and everything turned on again and ran smoothly....

I'm not very knowledgable as some of you but to me that seems like the Power supply can't handle the card. So hence my question....any idea what else it could be?

from my calculations about 12 amps. (takes 75w from the pci-e bus max, 75w form the pci-e 6 pins max)