how can i fix this problem?

I had the same problem and I did a factory reset.
-Turn TV off with remote
-Press INFO, MENU, MUTE, POWER ON buttons in sequence.
-The technicians menu appears. Carefully scroll down to 12.RESET and press Right Arrow to select. Do not select anything else or the results could be catastrophic!
This will reset the TV to factory settings and erase all channels etc.
-Turn the TV back on and perform a Plug And Play clean installation. It should happen automatically when you turn on.
Apparently this is quite a common fault and this should clear it.

Martin Lock
September 2009