See if iMovie still crashes with a new movie and imported footage, just make a quick test.
I had a problem once where something happened with my Media folder. The program would crash and act strange so I made a new Media folder copied all the files into it and then trashed the old one... it seemed to work for me but I can not remember the specifics of my problem.
I would start by just making a new project and import a few files and see if it crashes.
good to hear that you got it working! imovie is a bit odd, my issue only happened once and it was with a project over 30min long. since then i have purchased final cut and now only use imovie for short movies, mainly for the web.