I had an older 55" that would turn off quickly after being turned on. Not to mention occational red and blue color bending for about a year before that. From what I read I think it was the convergence IC's (controls the red and blue colors or something), which can go bad or the soldering on them can come loose causing shutdown. Then I moved the TV, probably correcting some loose soldering, and it worked again.
Check here...
http://www.tv-forums.com/forum/TV_Eq...pair_Forum_F3/