I have the same problem with my 42" LG. From what I have read online, the problem is with the YSUS (or Y sustain) board. I have also read that the ZSUS and YSUS boards must be changed at the same time, but there has not been a consensus on that. The boards vary in cost. My YSUS costs $106. I have found this website to be comprehensive and well priced: http://www.partstore.com/
Good luck.
Kim
August 2008