Samsung LN52A580P6FXZA HDMI Problems

I have a Samsung 52" LCD model number LN52A580P6FXZA that is having some HDMI problems. I recently bought a Sony Blu-ray player BDP-S570, and when I turn it on and switch over to that input, the TV will flip back and forth between showing the signal from the Blu-ray player (device menu), and showing the "No Signal" screen.

Also, when I plug in my computer via HDMI to MiniDisplay port, the TV sometimes will just not want to display at all, sticking to the "No Signal" screen. I have tried different cables and different ports, and seem to be having the same problem. It almost seems random about how it happens. Sometimes I can plug in the computer and it will work just fine. Other times, it just won't work at all. I plug in the HDMI to the computer, and the computer screen will go blue for a second (which is what it does when you plug in an external display), but the TV won't show the signal.

Does this have anything to do with the way the signal is carried over HDMI? It's like the TV just sometimes doesn't "see" the device on the other end.

It's an older TV, maybe 2 years. I'm not sure if it's still under warranty, but I'll check. I did buy the extended Best Buy warranty, and have already used it once. Had a lightning strike a year ago that fried a single HDMI port on the circuit board. Technicians came out and replaced the board.

Is this sort of thing common? Has anybody else experienced this with a Samsung?

I've never been one to believe in high quality HDMI cables, but maybe I should go that route. All my cables from from Monoprice and run about $3 each. I never have a problem with the signal from the DirecTV receiver, but the Blu-ray player and computer have issues.