I recently updated to 12.10 and made the jump to 13.04 shortly after that. Unfortunately, Handbrake refused scanning DVD due to an error in libdvdnav. Apparently something went wrong during the dsitribution upgrade. To get libdvdnav and Handbrake working again, just run:
sudo /usr/share/doc/libdvdread4/install-css.sh
Restart Handbrake and your DVDs can be read again….
Brain/Drain/Pain 