Do a reset to this set and check. If it do not help you, make sure that the firmware have corrupted.
To do a
hard reset, just unplug the TV from AC mains wall socket, and re-plug it back after 15 minutes or so. This procedure will make it a hard reset. If you want to make it a
system reset [Factory Reset]; you have to enter its service mode option, and select the factory reset option. If you wish to get some details; check the site linked here.
Pull up older posts. Surf the site with patience.
http://electronicshelponline.blogspot.com/
Service mode entry, adjust and exit procedure to many popular brand TVs are given. Never forget to exit the service mode, after all adjustments have been done.