I had the problem that xfburn was unable to detect my external USB CD/DVD burner. The problem lies in UDEV wrongly identifying the device with ID_TYPE=floppy. See this bug: http://www.mail-archive.com/debian-b...msg971826.html
Luckily the problem can be solved with an additional UDEV rule:

1. sudo nano /etc/udev/rules.d/70-persistent-cd.rules

2. There should be a block of rules for your external writer already. These rules automatically create symlinks in /dev. Now add another line like this:

SUBSYSTEM=="block", ENV{ID_CDROM}=="?*", ENV{ID_SERIAL}=="xxxxxxx", ENV{ID_TYPE}="cd", ENV{GENERATED}="1"

The trick is ENV{ID_TYPE}="cd" what tweaks the devices identification.
Do not forget to replace ENV{ID_SERIAL}=="xxxxxxx" with your devices proper serial (check the other rules in the block).

3. Save the file (Ctrl.-x), unplug the device and plug it in again.

4. (re)start xfburn and the device should be there.