Cannot burn CDs any more

[Uqbar]

While I can burn DVDs both from an ISO image and from a file collection, I cannot do the same with CDs and CD-RWs.
K3b said I could have problems with file permissions for both the executable helpers and the device file in /dev.
I applied the suggested changes. But still cannot burn any CD.
I attach also the k3b log file.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: k3b 2.0.2-3ubuntu4
ProcVersionSignature: Ubuntu 3.2.0-23.31-lowlatency 3.2.14
Uname: Linux 3.2.0-23-lowlatency x86_64
ApportVersion: 2.0.1-0ubuntu11
Architecture: amd64
Date: Wed Jul 18 22:18:00 2012
InstallationMedia: Kubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120424)
SourcePackage: k3b
UpgradeStatus: No upgrade log present (probably fresh install)

[Uqbar (uqbar)]

It's wodim!
wodim is not able to burn an ISO image any more!