There is not enough space to burn this compilation to disc- Nero Vision?

Recently I burned an avi file (actually two), to a standard DVD-R using Nero Vision 4. But now when I try to burn only one avi file that is only about 789 mb, I am having problems. The Nero Vision bar says 4.36 of 4.37, good. After almost 3 hours of encoding, the disc pops out saying, there is not enough space to burn this compilation to disc, please insert another disc that has enough space. I have tried more than 5 times with different methods. Has anyone ever had this problem, and how do you fix it. By the way I am using Nero Vision 4 and Nero Startsmart 7. All help is appreciated