Yup, same damn problem here...X700 ATI card. I switched complete machines over this damn mess, went to a Nvidia 6600 (like it a lot btw), and will never buy another ATI card as long as I live. Never saw this thread until it was too late, so I thought I was the only other person on the planet with the problem. I posted it here (another forum topic), only got one response, and on AVS Forum (no responses), so I figured it was me. I had returned the card (almost brand new) and got a new one..no diff. Went to a major computer place and plugged my box into about 4 diff brand HDTV's, no Diff., etc. Still thought it was just me and my bad luck as no one was responding to my post about it.. now I see why! It was in a diff forum! (btw, I did search like heck for anything to do with ATI and never got anywhere near this thread!)
Anyway, I still have the box, WITH A BRAND NEW X700 still sitting cold and unpowered, so it would be nice to get a fix, but after a month it is not even fixed, so I can't see where ATI's priorities are at all. Maybe not enough voices are being heard. I will throw mine into the mix, but am not too hopeful. Good luck all, this cost me $2200.00 (new media box, did not know it was just simply an ATI problem or would have just bought an Nvidia card!), so if you got off cheaper, consider yourself lucky! Damn ATI! 
P.S - Oh yeah, my HDTV is the new A10 Sony RPLCD set, just FYI...