My Epower 550W with 40A struggled with this card. They are beasts when it comes to power requirements. Did you plug into the the 6 pins FURTHEST from the 6 pin power, or the 6 pins CLOSEST to the other 6pin PCI-E slot?
You have to plug into the one thats furthest from the 6 pin, so there is a gap of 2 pins in between the two plugs on the card.
The pins will only go in one way, if you take a close look at the female end of the connection each pin connector is shaped different. Thought this might help.