I've had the same problem in K3B in both fc3t3 and fc3rc3: I'm trying to burn a DVD with just 2 files: a 4.1 GB tar file and a 7.8MB tar file. I've burned about 4 other disks today and they all work fine. K3B starts setting up to write like it normally does. Then the overall progress bar jumps to about 75% and displays a ridiculous volume of data written. It appears that K3B resumes to normal writing after that. The disk finishes at a normal pace, but it is a coaster because the first 80% of the data didn't actually write. I've made 3 coasters today trying to write the same data: 2 in fc3t3 and 1 in fc3rc3. It acted the same way in both.