Hi there ahurd,
Can you tell me, is the box "Only Create Image" a checkbox that you can untick?
If yes, then try the process again without this box checked.
If this box is checked then K3B will not automatically burn the CD for you, you have to do it manually (as you discovered).
If this does not help, it could may be a permissions issue.
You can try running k3b as root:-
And then running "K3b Setup" from the Settings menu. This will sort out a lot of things.