Editing Clips in iMovie Event Library in CineForm

Backround: Before knowing what I was doing with my new GoPro this winter, I immediately imported all my clips shot with the GoPro into iMovie. As I've learned since, I need to use CineForm studio for utilities that iMovie doesn't offer. In this case, I'm looking to cut down the length of the event clips (I leave the GoPro rolling, the clips are 30+ minutes and I need only a few short segments from the entire clip) into smaller parts and ditch the excess.

Question: When I open CineForm and try and select the clip in Event Library, CineForm will not open it for me to edit. Any ideas how I can fix this? I imagine it has to do with the file types (.mp4 vs. .mov)?

Thanks,

Steve