If it's new you should be under warranty.
If not, you need to replace the Power Control Board 6871qch038a
My Plasma is a VIZIO P42HD but all the components are LG.
Spoke with PartStore.com, rep stated 6871QCH038C (038C) is the superceded replacement for the defective prone OEM 6871QCH038A (038A). They and others offer the 6781QCH060Q (060Q) for $50 - $100 more. I opted for the 038C, but I was concerned about the title of the part which states "HAND INSERT"... PartStore.com rep stated it is in fact a board and there is no soldering needed, just "plug and play". DONE, paid only $120.95 + next day shipping for $29.95.
Since I took the TV apart before, it was a breeze and took about 2 hours, start to finish.
Important note, remember to remove the two 1" square spunge type heat sinks/pads the new board needs those for a proper installation and protection of the certain component.
Also you need two small zip ties to replace the ones you are going to clip off.
Added Bonus, the new board fixed other issues:
1. At times I would get a squeegly red line go across the screen. I thought it was the source (cable) but it is gone now.
2. Screen Shift, when I use the XBox for Games or DVD/HDVD the screen would shift. Very annoying, prior to swap out, recently the screen started to shift watching cable. Now it is no-longer an issue.
I am really pleased with my DIY repair and wanted to share.
The damn Vizio Out of Warranty Service wanted $360 for a service call which included the part for $125 plus they take my bad board for exchange.
6871QCH038C $120.95 http://www.partstore.com/Part/LG+Electronics+Incorporated/LG+Electronics%2fZenit h/6871QCH038C/New.aspx
Over Night Shipping #29.95