ok, found the solution. this isn't really a bug in k3b. i was writing to a fat32 partition. the image creation didn't complete because of the 4GB limit on fat32 files.
however, there is a bug in the fact that k3b crashes madly instead of giving an intelligible report on the problem. compare its behavior with the seemingly not user friendly dd: dd if=/dev/hdb of=dvd.iso File size limit exceeded (core dumped) -- k3b crashes midway through creating dvd image https://launchpad.net/bugs/83609 -- kubuntu-bugs mailing list kubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/kubuntu-bugs
