I've got a Panasonic A110 that has been trouble-free for years. Now all of a sudden it won't open its door for me to insert a DVD. It powers on normally, but when I push the door button nothing happens. When I hit the power button again (as if to switch it off), the word "Locked" appears on the front panel display. I went through the manual on the web site and I can't find anything about this mode. I thought it might refer to the hardware plastic key lock that it ships with that prevents the tray from sliding around during shipping, but the key is not in place (obviously). Perhaps the sensor for that is broken.... Any suggestions would be appreciated.