Toshiba RD-XS35 won't play some disks

[inferno7]

My Toshiba RD-XS35 HDD recorder which I've owned for almost 2 years now has suddenly stopped playing some DVD disks. These are store bought movies which I've played previously on the unit with no problems but for some reason now comes up with the message "disk empty". They play fine on my friends' DVD players so I don't think it's the disk. I've tried cleaning the heads and leaving the unit unplugged for several hours to see if that would fix it but it didn't. Again, it's not all disks just some ... any help would be appreciated.

[solarfox]

How many hours of use has it seen in those two years? Laser diodes only last so long, and if you've made heavy use of it as a recorder, it might just be wearing out. (Recording requires much higher power output, which shortens the laser diode's life vs. playback only.)