Here some useful (?) details & logs:
The device is listed in the hardwarebrowser as ATAPI CD-RW 52x24 Device: /dev/hdc
That's perfect, at least it was.
The log for "nautilus --no-desktop burn:" is:
cdrecord: Illegal write mode for this drive.
cdrecord: Drive does not support TAO recording.
SCSI buffer size: 64512
cdrecord: Warning: using inofficial libscg transport code version (schily - Red Hat-scsi-linux-sg.c-1.80-RH '@(#)scsi-linux-sg.c 1.80 04/03/08 Copyright 1997 J. Schilling').
Linux sg driver version: 3.5.27
Warning: Open by 'devname' is unintentional and not supported.
scsibus: -2 target: -2 lun: -2
devname: '/dev/hdc'
scsidev: '/dev/hdc'
cdrecord: WARNING: This causes a high risk for buffer underruns.
cdrecord: Permission denied. WARNING: Cannot set priority using setpriority().
cdrecord: Operation not permitted. WARNING: Cannot set RR-scheduler
cdrecord: WARNING: This causes a high risk for buffer underruns.
cdrecord: Cannot allocate memory. WARNING: Cannot do mlockall(2).
cdrecord: Continuing in 5 seconds...
cdrecord: Future versions of cdrecord may have different drive dependent defaults.
cdrecord: Asuming -tao mode.
cdrecord: No write mode specified.
I do not have a clue, because it happens just with this kernel, and I don't find any information about that problem with the 2.6.8-kernel through google.
Thx Markus