ive had the problem many time or at least often enough.
quality of your laser lens has a lot to do with color dyes on your disk.
if ya burned many times with a gray for example and now then won't work the you might want to clean. use canned air static free. open the cover and lightly spray across the lens with door open.
if you have new disk with diffirent colors red, blue dyes and they don't work then don't buy them no more. on the other hand you can buy disk and get to good a deal they may be getting close to expiring. stick with the colors that work. if your still having problems then try changing to a lightly slower speed.
about a week ago i had issues with burning a particular duel layer data dvd.
my issues was not related to none of the above. i went from nero 7 to 8 to burn small files. about 6.g (160,000 files). they were burned as data iso and image.
i know, it can sometime be a pain in the ass. .... good luck.