I spent hours last night trying to burn an image to many CDs and DVDs using Brasero. Basically, Brasero sucks. I seem to remember it working several Ubuntu version back, but as of 11.10, anyway, it just burns coasters like a furnace burns coal.
So anyway, try using some other cd/dvd software. People seem to think k3b from KDE works pretty well. I myself am looking for another app to use in GNOME. GnomeBaker is out of the repos as of Oneiric, it looks.