In this case we had a problem with iMove not sending videos to iDVD on a new MacBook Pro. My wife struggled for a while trying to figure out the problem and so did I. Then, I realized the problem was one that I had created.
For my wife’s birthday I bought her a new MacBook Pro. She had been using an older G5 iMac. When I setup her new laptop I transferred her home directory and her applications from the iMac.
What I wasn’t aware of was that this ended up providing her with two versions of iMovie. One had been copied from the iMac and was much older than what came with her new notebook. iMovie couldn’t send videos to iDVD because it was an older, incompatible version (while iDVD was the new version). If the application names and locations had been the same it probably would have only kept the new version but there was a slight difference.
So… if you transfer to a new Mac make sure that the program you’re using is actually the more recent version.