Recently my MacBook Pro's SuperDrive would stop buring DVDs. It would try to 'open the session' and then fail with an error message which said that it cannot calibrate the laser for this medium. Putting in a different type of DVD did not help. A restart of the computer helped once, but that was just by chance. Burning CD still worked OK.
Apparently dust on the lens is the problem. This very good page describes how to remove the SuperDrive and disassemble it and clean the lens. But the procedure is quite involved and often there is just a bit of dust on the lens, just enough to make the burning fail.
I read through the comment on that page and looked at the pictures. Apparently a lot of people were able to clean the lens by using a thin credit card like thing and a dry soft cloth for cleaning glasses. I tried this as well and it worked after the first try! Burning DVDs works again. There is probably no control over the amount of dust removed by this procedure, but as long as one can remove enough dust to make DVD burning possible this is OK with me as the cleaning process just takes 1 minute. :-)
Obviously you should never do this if you are afraid of destroying your SuperDrive. There are delicate mechanics in there which could easily break.