Sorry to be negative, but I also bought an Asus P5K (premium black pearl).
Same problem, turns on, everything sounds like its working but no video.
Typing "P5K no video on boot" into Google says it all.
I know every now and then someone has to have a dodgy/duff board, but i'm extremely disappointed, and I don't feel like having another Asus board.
I know it's possible a replacement might work fine, but with the amount of people its happened to, and the different situations, I wouldnt feel comfortable each time I turned off my pc.
What surprised me most was the lack of knowledge of this particular problem on the forums. Not in a bad way, everyone is very helpful, but in my opinion it's a reason to avoid buying an Asus board.
All this said, I always get frustrated and make a mountain out of a molehill, I'm sure there are lots of people sitting there right now with the same board as happy as can be. Damn you!
OP - I feel/felt your pain