I've not heard of this problem.
(If you haven''t already, first try the TV with the DVD completely disconnected.)
However, if there has been corruption of the memory data after connection of external equipment, most Panasonic TV's (in U.K.) can be reset by the following method... (sounds like yours is US model so I can't say if this will work for you.)
On UK models it is done by turning the Bass control to Maximum setting, the Treble & Volume to Minimum then press ('F') button and at the same time the Volume Down (V) on front of the TV, then while pressed hit the status button (+) on the Handset. If it works you will get Test Mode, while it's displayed,.. power off at the TV switch.
Whether or not this info. is compatible to US models I don't know.
Cobweb
December 2004