Just got a PS3 Slim 120GB (actually, have had two now since I returned one). The issue is that at random times during games or playback my TV screen will flicker black for a split second. I've tried 3 different HMDI cables and two systems, all causing the same issue. Even more peculiar is that the issue slowly goes away the long the system is on, although it really never fully disappears.
I've tried Sony support but they're taking forever to get back to me, so I figured I'd turn to the group that knows how to fix everything (at least all the problems I've ever had).
Just as a heads up to anyone facing similar issues, I did find a temporary (or maybe permanent) work around. In the output settings of the PS3 I turned off 1080p output but kept output at 1080i. From what I've read, my TV will automatically convert the 1080i to 1080p regardless. For whatever reason, turning off the 1080p output has fixed the flickering issues.