iMovie trobleshooting help required.

iMovie has gone from being reasonably reliable to very, very flakey on one of my machines. It seemed to start after my iMac hung while importing fotage frommy NEX-VG30.

Now I have a number of problem;

• iMovie keeps crashing
• iMovie won't open a camera import window
• iMovie won't see my NEX-VG30 although it never used to have a problem with it

Anyone have any suggestions for trouble shooting these problems?
iMovie 9.0.9 on OS 10.8.5