I have the same problem with a Radeon HD 5750. Tried all the solutions mentioned here. No Success.

Also used the opportunity to connect the SATA power cable to the Motherboard - did not resolve my problem.

Has anybody actually got a Radeon HD 5xxx Card to work on this motherboard?

I had the same problem but with a different video card.  I mean exactly the same problem, no keyboard and no video with the Eb code displayed on the POST LED.  I am guessing that you have two memory modules installed on the motherboard.  As it turns out one of my 4 GB DDR3's died.  I removed the dead one and everything got better.

Good luck

Chris