Categories aren't working.

[Strawberry85]

So I've finally managed to move my database to my new one and got the gallery online.
But now the categories aren't working. I get this message:
Critical error, unable to retrieve data from the database.

The albums and everything are working perfectly, but the categories are not. I don't know how to fix it.
I am able to create new categories, but I don't want that. Since I have many albums that were already assigned to the categories.

[Αndré]

Please post a link to your gallery and enable debug mode for everyone.