I don't know why, but just now, I tried to burn a few .mov files onto a dvd and it won't work, I get the following error. HELP!! Oh, and yes, the drive reads, but won't write.
I had that problem quite a few times. My most recent success was getting a CD lens cleaning disc (those with little brushes) and use it to clean the lens, after which made it write to discs again. You may try and see if that works for you.