iMovie 6.0.4 suddenly crashes constantly
I have been using iMovie 6.0.4, running OSX 10.8.4 for a long time. Suddenly about 3 days ago, I can only have it runing for a minute or two before it crashes, even if I'm not doing anything.
If I log in as a guest user it seems to work fine. I know that means something in troubleshooting the problem, but I forget the next steps I need to take.
If I remember correctly, I installed an update to FCP recently which might have something to do with it.
Thanks
OS X Mountain Lion (10.8.4)