Why can't I consistantly burn xvid, divx, avi to a data cd successfully?

I burned maybe 3 or 4 movies successfully using Nero to burn the files to a data cd. I slowed the burn speed down to 16x to try to ensure a decent quality and successful copy to play on my dvd/divx player. I have found that after burning these few discs for some reason (using the exact same method) my computer no longer carries out the task successfully. One drive seems to fail mid-way through burning and the other seems to complete the disc but is out of sync when played.
Does anybody know a solution for this as I am wasting many discs and it's really frustrating.