Hello Melissa,
I've just recently come across the same problem. I've read of a few solutions found using Google, but this is what worked for me.
Hold the power button on your remote and the stop button on the front panel for about 4 seconds. Nothing happened for me at this point, until I repeated it. Immediatly the lock came off. It's definetly something to do with the power and stop buttons.
Other than a guy selling DVD players not wanting a disk in a display machine getting stolen, I can't imagine what this function is useful for.
Anyway, I hope you're able to figure it out. Especially if, like me, the disk that's stuck is a rental *lol*
Ted, September 2007