I have the same problem.
50% of the time my smasung 46" makes a buzzing noise for a few seconds before clicking and losing picture. I still get sound, and sometimes it turns on and works no problem.
I've taken the back off but cant see any bulging capacitors. It sounds very much like the problem described in the thread about the 40" samsung LCD but just wondered if anyone had any specific advice for this model, or knew if I might be looking at a different problem given presence of sound and absence of bulging capacitors...
Joe, August 2009