There are two things that can cause this, the first is a buffer board and the second is the plasma
panel. That is assuming the two are related, which given the succession of events, they probably are.
That said, it may be repairable, but may not be. The buffer board normally runs around $200-300 to have replaced by a tech, however, if the panel is bad, the part alone costs more than a new tv.
Normally about 80% of the time, the panel causes this problem and about 20% of the time it is the buffer board.
So without some troubleshooting or replacing the board its pretty much impossible to know which one is causing the problem in your set though.
Please let me know if you have any other questions or need any other information at all, if you do please use the reply to expert tab. If this was all the info you needed then please remember to rate me before leaving. Please do not hesitate to ask anything, happy to help in any way I can!