I'm trying to capture a video on iMovie via my built-in iSight. It is coming out to be about 20 minutes long. When I start, it says I have 487 minutes worth of space on my computer. It will not generate thumbnails or acknowledge that I recorded anything except an empty file under "events" with my title. How can I remedy this situation? I'm not computer savvy, I just want to send a video to a friend!