I'm trying to burn a movie to a dvd...

I've added the movie to a playlist, and then I select "Burn playlist to disc" from the file tab. My problem is that when I do this, it continually asks me what I'd like to do with the disc (and won't actually burn the movie). I get this notification both from iTunes and my computer. The dvd holds 120 minutes, and the movie is only 80 minutes long, so that's not the problem.