I had the same problem when I upgraded cdrecord etc a while back.

IIRC
- Under K3B the writer shows up only as a reader.
- Works if logged in as root
- Even if you are listed as a user in K3B setup it still doesn't work

It was a while ago so bear with me as I try to remember........................
I think it had something to do with permissions. Something was changed
when the newer version was installed!?

Let me know if it runs as root.

Good Luck
rob