I just got a DVD drive in my iBook and everything now works. Although there is one problem. When the dvd plays, when people move sideways, the things that are moving have jagged edges. What is wrong, its REALLY annoying.
There might be an option in DVD player called Deinterlace/interlace. That might be the problem.
If you're describing a problem like the picture above, then the 8 year old calculus student was right. It's an interlaced DVD, but there is no option in Apple's DVD Player to deinterlace it. Most DVDs don't contain interlaced video, so pop in a different DVD and give that a shot.