While attempting to burn a CD with K3b I was informed I did not have sufficient permissions. I was prompted to change permission on "cdrecord" and "cdrdao" (as I recall). After setting group ownership to "cdrom" (users were already members of this group) and reinserting the CD for burning, the CD automounted and the Device Notifier prompted me for action.
Not sure why those programs prevented automounting, or why group ownership wasn't defaulted to "cdrom", but there you have it.