This problem can happen due to several things. The power supply is a common cause of this problem. The capacitors on this board can swell and bulge due to receiving a surge, and can cause a voltage drop on one of the outputs on the PS. This typically will cost you $150 to have repaired.
The other very common issues, are problems with the Y Sustain, and Z Sustain boards failing. They are responsible for lighting the Plasma display and are common failures for this type of TV. The voltages need to be measured by an experience professional between the power supply and these boards, and also from the boards to the Plasma Panel. Average cost for this type of repair is around $450 parts and labor.
If these boards test good, then the problem is the Plasma Panel itself which will mean you need to get a new TV. The cost to replace the Plasma panel will exceed the cost of the TV itself, as the panels are very expensive and very labor intensive to replace.
I wish I had better news, but the set will require component level testing and replacement in order to function properly again.
You can locate a tech using the link below:
If you need further assistance, let me know.