I'm receiving a message trying to open an old backup library that the library is damaged and can't be updated. I have some projects on the backup library that aren't on the original library (don't ask). I would like to retrieve them but don't know how. If I start a new library, can I somehow import the projects from the damaged library (they are visible in the Original Media folder). Or is this the wrong way to go about this? Not sure how to repair a damaged library.
Try using Pro Maintenance Tools project repair utility. It is usually pretty good at repairing corrupt projects and events that live inside the library. If you don't own it, I believe Digital Rebellion still offers the 10 day fully functional trial, but it's an app that's well worth having.
Aside from that, you might try manually deleting the render files folder inside the library thru the finder and then test if FCPX will open it successfully.
Additional info UPDATE: You can also try to select the library in the finder and right click to show package contents. Then you can selectively copy a project or event to another location. If you have many inside the library, try one at a time to see if you can get one to open.