If you think that iMovie would easily work with .mov files (e.g. drag and drop) like I did — you will be unpleasantly surprised. However, this workaround was successful for me.
1. Drag the .mov into iPhoto (yes, iPhoto).
2. Drag the .mov FROM iPhoto into an iMovie event.
Now you should be able to work with your clip. This procedure may not work for all .mov files as there are many different codecs behind .mov’s, but this is a quick and easy solution you can try. Feel free to comment if you have more suggestions or a faster way.