I seem to remember that older versions of k3b were quite buggy, so I quit using it.
Though it will probably be ugly to you, give the command line a try.

First open up a console in which you type
<code>
sudo su -
</code>

Next, you need to determine the hardware driver:
<code>
cdrecord -scanbus dev=ATAPI
</code>
Leave "dev=ATAPI" out if your burner is SCSI. You will see strings like
0,0,0 0) 'HL-DT-ST' 'DVD-RW GCA-4080N' '0H38' Removable CD-ROM

In this case the device is "0,0,0" and we'll need it for the burning command.
Now mount the partition you want to save data off by clicking its icon or by entering
<code>
mount /dev/hdaX /mnt/hdaX
<code>
and replace X with the appropriate number. Also substitute sda for hda in case of SCSI.

We're now ready to roll:
<code>
mkisofs -J -r -v /mnt/hdaX | cdrecord -v -pad dev=0,0,0 -
</code>
The symbol between hdaX and cdrecord is the "vertical bar", not a "one" or an "ell".

Now pray and wait. If your burner is ATAPI, you might want to try "dev=/dev/hdY"
with Y=(a|b|c|d) (probably c) instead of "dev=0,0,0".

HTH