In early 2006 my DMR-ES40V changed it’s viewer ratings on its own, locking up the machine so that it would not play any DVD. It gave an error message.
The DMR-ES40V had reset the “rating” by itself to a low number (1 or 2) that is very restrictive. When I attempted to change the “rating” back to the “8” default (in the FUNCTIONS, OTHER FUNCTIONS, SETUP, DISC, SETTINGS FOR PLAYBACK, RATINGS) I was asked for my password. I was the only user of this machine and I had never set a password. Nothing I tried would allow me to use the machine.
Here is the workaround provided by Panasonic: Power unit on. Open DVD tray. Press and hold REC and PLAY on the machine for over 5 seconds. If done correctly the DVD tray will remain open. The ratings password setting will return to the default (no password). The rating will return to the “8” default.