I just discovered a huge bug regarding custom menues in WordPress 3.01. If you accidentally name a menu with an existing category name, and then rename the menu, you will end up also renaming the category.
In my case I wanted a menu containing my blog posts about SEO (Sökmotoroptimering in Swedish) so in order to make things simple, I named the menu ”Sökmotoroptimering”. After populating the menu, I realized that it would be confusing in the future and re-named…