PLV3122GB. The screen turns on OK and stays on for 15-20 minutes, then shuts off. If I power off and turn on again the same thing happens.

Only one bad door switch should do that

The 20 min time out is the GEM or Body Module,
which is normal only because you have a bad switch,
otherwise it goes to sleep when either front door opens

Put radio on & open a door,the radio should go off
& kill the time delay if no issues exist

If you turn your monitor on and when its on you go into your computers settings. Where you can fix your monitor and fix the resolution and all that. There should be a thing there where you can put never shut off. You have it on 5 to 10 minutes to shut off. That will keep the monitor from turning off again. I did this with mine it kept shutting off to. Thanks for posting I hope this helps you. I am sorry I couldn't be more detailed. i have been up all night lol.

Does the power light stay on? If so, you have an inverter problem. If the power light goes off, you have a power supply problem.

Boot up to the safe mode screen & select last known good configuration.

I ended up exchanging the TV for a new one that works fine.

Most likely the TV is detecting an internal problem with it's circuitry and is shutting itself off to prevent further damage. You'll need to have a professional look at your set to determine exacly what's going on. Aside from leaving the power cord unplugged for five minutes, then pluggin back in and trying it again, there's nothing anyone can do from here. Sorry.

Hope this helps, and please rate my advice, good OR bad.

Good luck!

i had the same problem, apperantly creative made an error making the hardware for the subwoofer, and put in an mos-fet with to little resistance, i called creative and gave them the serial number behind the subwoofer and they sent me a new one that hasnt acted up yet.

upgrade to the latest firmware
http://us.creative.com/support/downloads/

Since mine was only a day or two old, I took it back to the store and got it replaced. Since then, it's been fine. Hope you have the same option.