Frozen playback in specific clips on Timeline

I'm editing a 40 min movie, and while I'm browsing on my timeline, there are a few clips that won't show on the playback. The sound works, but the video won't play. On the playback screen shows the last frame that wasn't frozen. everything before and after those clips seems to work just fine.

I've tried closing and restarting, disconnecting the hard drive, creating a new project, re-importing the clips to the timeline... nothing. About 5 minutes of the timeline refuses to play. All the clips on the timeline are from the same camera, same settings, same import.

The only thing that has changed is that I've updated my FCPX today.