17" Macbook Pro, noticed that burning DLs was hit or miss, mostly miss. Took into an AppleStore for repair. They replaced the drive but that did not improve the situation. They said, "aha, it's either the flex cable (unlikely) or the motherboard (VERY unlikely) or software." So, they did an archive/reinstall of OS 10.6 and, hey, guess what! 100% success. I let Software Update do it's thing: a print driver update, a composite system update, and a safari update. And, hey, guess what! It still works.
ARCHIVE/REINSTALL SYSTEM OS! (Don't forget to backup your data... just in case.)
Why nobody knows about this is beyond me.
good luck, all.
--ken