If your computer has only gone to Sleep mode since this problem, select Shut Down in order to refresh the system.
Instead of sharing to iDVD, share to Media Browser. Use the Large setting if you are using the optical drive in your mac.
These suggestions are starting points. You may have other issues based on the complexity of your movie which you haven't mentioned.
Yes, I had already shut down and restarted many times. Also, from reading earlier posts to other questions I was sharing to Media Browser. I began to "deconstruct" the project. When I removed the bulletin board theme and went back to "No Theme", the project was able to be shared. So, although I am now able to burn the project, it is not the project that I wanted to burn. Must be an issue with the "themes?" Just speculating. Also, there must be something else going on because I am getting lots of that spinning wheel thing while it thinks.