problems with imovie

Hi Folks,

To date I've been successfully using Imovie to import and edit AVCHD video from my Sony HCR-CX6. Recently I was half way through an import and a software update was flagged. The Mac locked up and I had to force a power off. Since then Imovie can see the camera but I'm getting a blank window in the box where you choose the clips to import ie I can select the camera or the camera archive but it won't let me see the clips. I've updated to the latest vesion of Imovie but it still doesn't work. Current solution was to use my sons Mac to import and create the 'event' then copy it back on to my Mac. Imovie will then see the new event..... Wasn't supplied with any system discs when the mac was new, so can't just reinstall?