Shot in the dark but here it goes.. what kills Plasma's is heat, and they are typically fan cooled. feel that part of the screen front and side/back if possible and compare it to another part of the screen that is fine.
What source are you feeding it? Check with a DVD over DVI or HDMI if possible since this is a digital device.
Otherwise it could be a power problem (move you audiophile power filter/conditioner over to the plasma and check again..)
Otherwise ask this question on the www.avsforum.com if you don't get enough answers here.
Chris
