Software was updated today at Apple Store, and now can't access photos and videos in iPhoto

Question

I brought my iMac into the apple store today as I was having issues with programs freezing.  They wiped everything clean, reinstalled my programs and updated me to the current version of OS.  After I transferred my info back in from my back up hard drive, I went into iPhoto to check to make sure everything was ok.  I got a message stating that I had to update iPhoto to work with the current software to be able to view/use pics.  I clicked ok, and everything updated.  When I now go to iPhoto, all of the events are labeled correctly, but all but 2 are black with no key photo (even though I designate one).  Basically, the screen is all black with all the blank black event squares.  As I scroll down, the key photos will appear for 1 second, and then disappear.  When I go into the event, I see all of the photos very small, and when I try to enlarge them or click on them to edit or view, I get a triangle with an exclamation point in the middle of it.  When I click on any movie/video, I get a message saying that "the movie contains an invalid data reference".  I have about 8,000 photos.
What is going on and how can I fix this?????

Answer 1

The ! turns up when iPhoto loses the connection between the thumbnail in the iPhoto Window and the file it represents.
Option 1
Back Up and try rebuild the library: hold down the command and option (or alt) keys while launching iPhoto. Use the resulting dialogue to rebuild. Choose to Repair Database. If that doesn't help, then try again, this time using Rebuild Database.
If that fails:
Option 2
Download iPhoto Library Manager and use its rebuild function. (In Library Manager it's the FIle -> Rebuild command)
This will create an entirely new library. It will then copy (or try to) your photos and all the associated metadata and versions to this new Library, and arrange it as close as it can to what you had in the damaged Library. It does this based on information it finds in the iPhoto sharing mechanism - but that means that things not shared won't be there, so no slideshows, books or calendars, for instance - but it should get all your events, albums and keywords, faces and places back.
Because this process creates an entirely new library and leaves your old one untouched, it is non-destructive, and if you're not happy with the results you can simply return to your old one. 
Regards
TD