i thought the command is:mount -t file system(ext2,vfat,iso9660) device(/dev/cdrom,/dev/fd0,/dev/scd0,etc.) mount point(/mnt/cdrom,/mnt/floppy,etc.)-in your case
mount -t iso9660 /dev/scd0 /mnt/cdrom
the directory cdrom has to exist in /mnt(it may be /cdrom depending on your setup)
mount cdrom should work if the cd device(/dev/scd0),the file system and the mount point are identified in your /etc/fstab-look at it and see what it says.