I'm using Opensuse 11.1. And it refuses to eject a DVD data disc I have inserted. This is the method I used to eject it.
First, find which processes are accessing it using the lsof command (lsof stands for list open files.) On OpenSuse 11.1, I used:
This gave me the PID of the "offending" process. Which I was able to kill. Then eject as normal.