Or maybe your ISP has rolled back your database for some reason. These changes are all database stored, so if they ever "took" then they would still be in the database.
The other possibility is that somehow the images and albums seem "new" to Zenphoto. For isntance, if you had the album folder names (Not the title) in lower case then changed it to upper case on a Unix system this would be a new album, so none of the attributes made for the old lower case version would apply. This prsuemes you did not use Zenphoto to do the renaming--if you do that we know enought to preserve the metadata.