I wonder if there is a setting that deletes the project after it sends it to iDVD.
Have you tried saving the project before sending?
I made a video and then sent it to idvd to burn a copy.
when I went back to iMovie 11, the project library was gone, and when I tried to click on the project library button, it went grayed out. I could not shut it down, so I forced it off. This happened last week when I put a call into Apple support for help. We did a restore at a later date and that fix it. And now, I'm back to were I can't see my projects in the project library.