In my case I had to recompile the kernel in order to add scsi device support (scsi cdrom support), which adds module sr_mod (check with modprobe -l or lsmod if you already have it), since usb devices are accessed via scsi devices.
After that (make xconfig, make modeles_install) , reboot and mounted /dev/scd0 on /mdeia/dvdrecorder (or any other mount point).
mount -t iso9660 /dev/scd0 <mountpoint>
In some cases, depending on the number of usb devices attached, the device id may differ from scd0, being another number. In such case, use lsusb (figure out bus and device ids), /proc/scsi files, /var/log/messages.