My content library is grayed out in the top menu and does not appear in the sidebar. Cannot use.

My iMovie's (10.0.5) "content library" is greyed out as well in the menu bar. It does not even show up in the side bar. The content library is still there in iMovie 9. I recently updated Mac OS to Mavericks and iMovie updated itself. I am using an iMac (post 2007). I have tried a few things but to no avail yet. I closed iMovie 10, started iMovie 9, let it re-establish stuff, closed iMovie 9, found iMovieUpdated (not exact wording) files in Finder under User:Movies folder, deleted them, then restarted iMovie 10. I was hoping it would somehow reset itself, but no. I then trashed iMovie 10, logged out and back in, and updated back to iMovie 10 through the App Store: Purchases. No luck. I fixed permissions - no luck. Also, I am attempting to access the "content library" while in a project (not an event), since that is where I would expect it to show up and be useful.

I had the same disabled menu item just after importing a new video file in my fresh iMovie 10.0.7.

The problem is that you need to create a new movie project, then move your video file into that project and voila. Content library with Titles and stuff will appear.