10.3 update emergency

I just updated to FCP X 10.3 and now can't open a very large (3+ TB) library and critical project. When I try to open the library a window opens to say this library must be updated to work with this version of Final Cut Pro. I click OK and it starts loading and says it is backing up the Library, but then a new window pops up and says "the library could not be opened because an unexpected error occurred. The file could not be opened because it isn't in the correct format. "

Other much smaller libraries and projects updated and opened with no problem, but this big one is critical and I need to fix this asap! Can anyone help?

Hi David, welcome to the forums.

I'm sure you have made a backup of this critical Library before updating it?

R-click the Library in Finder and select "Show Package Contents". A new Finder window will open showing the root folder of your Library. Make a screenshot of this window and post it here. We need to see if there are any particular files at the root level that may cause this error to happen.

- Ronny

I'm having the same problem. I've converted about 15 libraries with no trouble but one continues to give me this error. The only thing in the show package window that is not an event are these files:
Folder: _AsyncCopying
Folder: _Temp
File: CurrentVersion.flexolibrary
File: Settings.plist