has no permission to open the device

I have tried burning a CD with both K3B and XCDRoast and always the same 
error.

The cue sheet gets sent, then the session is opened, nothing is written, then 
the session is closed and the CD write fails.

This problem is new! Likely since August, at the earliest. Burning used to 
work just fine.

The message K3B sends is:

"cdrecord has no permission to open the device"

I have not changed the permissions in any way and have selinux disabled 
(formerly, it was permissive, but changing it to disabled didn't solve this 
problem).

Does anyone know what is wrong?