Strange VOBU error message when trying to burn disk - please help!

I have been backing up and burning disks for awhile and never came across this problem. I got the files onto the computer fine and they play fine, but when I try to burn the disk in CloneDVD, it only gets about 6% of the way before this pops up:

Creation of DVD files was not successful:
PS 29 VOBU 3 1 VOBU 4 73216 137 TCE

Does anyone know what this means or how to get around it?
Thanks for any help you can provide!