iMovie 10 Slowness

I've been working on a project with many small clips and about 5 audio files. Things were fine one day, and then slowed to a halt the next. I gradually tried scaling the video back so I could export what I had. I removed part of the video and all of the audio files. My thoughts being I could then continue with the bulk of the project being in one larger file.

I feel like I've cleaned things up pretty well, and started a "new" project to continue my video, but iMovie is still crawling. I see an improvement, but I can't even watch the one clip in the current project in the preview screen to edit it. The preview just freezes.

I feel like I need to reset things, if that's possible. Any thoughts would be greatly appreciated!!