Were you able to get this resolved? I have the exact same issue.
I basically have a weird issue with the HDMI of a brand new AMD Radeon HD 6670 connected up to my LED 22inch TV via HDMI. What happens is that the screen goes blank and then brings itself back up again every 20 minutes or so. I was wondering if there's any way to resolve this really annoying mess. I can't play games too well because of it, when the screen flicks back on it I'm nearly dead from random monster attacks on WOW.