Ack! Portable DVD player can't play DVDs :(

I have a Panasonic Portable DVD player, model DVD-LS5. I stupidly left the device on with the screen closed, and running a dvd. Now, if I try to wach a store bought DVD, it says "This type of disk cannot be played. Please insert different disk." If I put in an audio cd, it plays fine, so I know I didn't fry the laser entirely. Anyone know if there is a simple fix, like a reset/reboot, or if I'm goign to have to pay to have it fixed. If it's the later, any idea on the cost? Thanks