iMovie keeps crashing when trying to share

I am running iLife '09, and created a small 13-minute video. I had just successfully shared another video last week, but this week, with a smaller video, the program keeps either: 1)crashing when I try to share to iDVD (or share a large file to MP4), or 2)giving me a message that the program was unable to complete the process due to both: error -50 and error -108.

I have looked at very old strings on this same problem (very old in computer terms - 2 years) and no one seems to have solved this problem yet. Years of software updates, etc.

I have plenty of hard drive space (239.32 free) and RAM (4G free).

After quitting all other applications and disconnecting my back-up drive, I was able to share creating a medium-size MP4, but I still need to make a DVD for those less fortunate with no iTV!

Any ideas??? Please help!! This is project is a gift, and even though it is only 13 minutes long, it took many hours to create!