That's a classic case of a corrupted database, and as it's from a back up it's not much use going with my next suggestion, which is to restore from back up.
Download iPhoto Library Manager and use its rebuild function. This will create a new library based on data in the albumdata.xml file. Not everything will be brought over - no slideshows, books or calendars, for instance - but it should get all your albums and keywords 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.