Topic: Can an HDTV's "HD" go out?

We've had an HDTV for a long time now (4 or 5 years, it's a plasma), and it has various modes.

TV - the mode where we can watch things in SD.
Component 1 - Xbox 360 is plugged in here (HD)
Component 2 - nothing plugged in here
HDMI1 - nothing plugged in here
HDMI2 - cable plugged in here (HD)
Video 1 - DVD Player or Wii is either plugged in here (SD)
Video 2 - PS3 is plugged in here (SD)

Why I ask is, all of the HD "modes" aren't working, but the SD ones are (it was like this when we turned on the TV this morning).

It's not the cable messing up, because we can still watch everything (just in the SD TV mode), & play the DVD player, Wii, or PS3 (because they're plugged into the SD "Video" ports, although the TV buzzes loudly for a few minutes on these modes, but then it's fine).

With the HD "modes", nothing works. We don't get image or audio on the "HDMI" modes, & on the "Component" modes we get audio, but no image.

BTW, everything is still plugged in correctly.

Yeah sometimes it might want to go for a quick walk to the shops or a few drinks at the pub and maybe pickup a stray on the drunken march back home

That's really strange. I can't think of anything that would cause that.
Have you tried using the HDMI and component cables with your other systems? Have you tried the other HDMI or component ports on the TV?
I know those are kind of obvious, but I just can't think of anything else.
What kind of plasma is it? Some settings might have been tampered with or changed.

Well, that's odd. When we turned it on today, it's working fine, like nothing even happened.

I just hope it was a random glitch, and not something that's signaling the end of it's life.

BTW, thanks to everyone who responded.

TV companies want your money. They program TVs so that they die after a while >:3

"Planned Obsolescence." Apple was busted a few years back for a massively unethical business model centered around this very thing. Electronics companies are notorious for it.