I'm not real familiar with Debian, but I'll take a shot at this one. When you mount your dvdrom(labeled as cdrom) does it work? Most likely, in /dev you have a symlink called cdrom. This is a link to /dev/hdc, assuming you're dvdrom is master on secondary IDE. You'll need to create a new sym link(/dev/dvdrom) to /dev/hdc. Then, edit your Fstab to reflect the new symlink (/dev/dvdrom). This should fix the problem.
Also, to save me some typing. Check out this thread
. You might find some useful info there as well.