Sometimes I have this issue with my HD monitor.
Unplug the tv, press and hold the power button. This drains any power in the TV and resets the assigned ports. Now turn on your PS3 and than turn on the tv. Change to the port you have the ps3 on. Hope this helps.
I had this exact same problem! Everything worked fine with an HDMI setup on my 46" Sony Bravia TV until after I played a bluray disc one night. I shuttoff the PS3 after the movie, and turned off the TV. A few days later, I went to turn the PS3 back on and got the black screen and no audio. I didn't believe it.. it worked for 2 years without any problems. So my first instinct was the cord, which I swapped out for one I knew worked. Still nothing. I tried the whole video reset by holding down the power button and listening for the beeps. Still nothing. I then borrowed a cord for the AVI connection from a friend (I seemed to have misplaced mine ) and the PS3 worked just fine through that connection. I tried resetting it to default to no avail. I then tried manually setting the video settings for HDMI... still nothing.
The solution for me, was a TV reset like Jimnay had mentioned!! I unplugged the TV, held down the power button on the TV for a little while. Then plug it back in. Before I started the TV, I re-plugged the PS3 back in through its regular HDMI port I had been using, and then powered it on. I then powered on the TV, and Viola! The PS3 asked to be hooked up in HDMI mode, it did a quick test, and came out with 1080p. Everything is right in the world again!
I'm guessing this problem came from some display settings from the TV to view the bluray movie. It always seemed to flicker and stuff before it displayed anything in that resolution.
Hope this helped. Thanks Jimnay. Come to think of it, I have had the same problem before with my computer monitors too. So I switched back to DVI