Glad to see this post helped a few others out. Two years later, I am happy to report my "Polaroid" tv has outlasted the original, with not a single lock up.
@ajstan99: If you still have the tv, try using codes listed for Polaroid or Mitsubishi. As far as to how I figured out the problem, I used a multimeter to test all the voltages on the set and determined power not to be an issue. Electrically, the whole set is fine. The firmware chip just seems to destroy itself over time somehow. If someone had the microsoldering skills, you could probably just replace that and be fine.
@stubbbone: You are correct, I fatfingered the model#s in that post, it is GT321XA / JL321XA
@dicepackage: My original JL321XA didn't support picture in picture, either. Makes me wonder if there wasn't a second revision of this piece of junk floating around out there?