Why is my iPhoto burn failing? I am trying to burn selected photos to a DVD and it keeps telling me that the burn failed:

I've tried rebooting and that helped the first time, but the second disk I tried to burn failed. What's up with this? How can I fix it? I am using iPhoto '11 (9.2.1).
Ok, so after taking the MBP to the Genius Bar, they ended up replacing the optical drive. Luckily it didn't cost anything, as it was under warranty. So, I had a faulty optical drive to blame for my problems.