I have used k3b for burning .iso's and it worked just fine. I tried to use the autoconfiguration and it wrecked my fstab completely. Also, it seems that alot of people have trouble using the "copy cd" function. It seems to start OK but then errors. I have been using xcdroast which seems to be working fine. I've heard lots opf good things about gcombust but cannot speak from personal experience. Perhaps others reading this can add their own input on a frontend for cdrecord. Here are two lines from my fstab

/dev/cdrom /cdrom iso9660 defaults,ro,user,noexec,noauto 0 0
/dev/dvd /dvd iso9660 defaults,ro,user,noexec,noauto 0 0

The second line was not there- I had to add it. The first entry is the name of the device "/dev/cdrom" The second "/cdrom" is the mount point Since you have a cdburner you need scsi emulation right? Well because the drives are now seen as scsi drives Linux calls them sd0 & sd1 So if you wish to call your drive something other than what Linux does you will need to link it. Example: on my system the cdrom is /dev/scd0, the dvd is /dev/scd1 so....

ln -s /dev/cdrom /dev/sd0
ln -s /dev/dvd /dev/sd1

To find out if it worked do a:
ls -al /dev/cdrom
This should be your output:
lrwxrwxrwx 1 root root 3 Mar 23 13:30 /dev/cdrom -> sr0
Same for second drive:
ls -al /dev/dvd
You should get:
lrwxrwxrwx 1 root root 4 Mar 24 08:57 /dev/dvd -> scd1

Now your drives have basically been renamed. This is very helpful if your add another drive and so that their names are easy to remember. Now that you have them linked you must make sure that your mount points (listed in my fstab as /cdrom & /dvd) actually exist:

cd /mnt
ls
Your output should be similar to this:
auto cdrom dvd hda1 hda4 hda5 hda6 sda1

If you don't have mount points you could make them like so:
(become root)
mkdir /mnt/cdrom

If your fstab trys to mount to a mount point that does not exist it of course won't work.

Now as to Knoppix stability- on my machine it's rock solid. I would suggest avoiding k3b all together. There are several other frontends for cdrecord, mkisofs & cdparanoia. Just install one of them if you don't like xcdroast.

As always - post back if you need more help.