Just wanted to share this experience to save headaches for any Drupal admins finding it difficult to update the Category module

If you have been getting strange behavior from Category, you are not alone. It's extremely powerful and robust and, as such, prone to easy breaking. It's one of those paradoxes of computer programming -- the more the program can do, the more intricate the code, the more buggy.

Anyway, if a search brought you here because you're banging your head against the wall trying to update this module, try this:

Disable the book wrapper in admin/build/modules.

It should work so you can stop banging you head unless that's fun for you.

General takeaway: You may have noticed that sometimes the more complex modules will not update properly when you run the update script. I have seen this with CCK, Views2, and now Category. If this happens, try disabling the helper modules and add-on modules for that module. Then update again.