I also have a very similar problem with LG Flatron Plasma tv model number RT 42px12x and I am getting coloured vertical lines. Started on the right side then moved to the left. last night the left side went black and then multiple rainbow colours and then black again. I know of others who have experienced the same problem. I believe it is a fault which stems back to the manufacture. Have contacted the manufacture regarding the problem with frustrating results.
Frustrated Purchaser, February 2009