In WordPress 3.0.1, my categories box is not showing up in the post edit screen?

I'm setting up WordPress for a client. It's version 3.0.1.

As I'm setting things up, it seems now that the category box (where you select the category you want the post to go into) doesn't show up in the post edit page? It was most definitely there before, but now it is not. I'm not sure what's happened?

I even reinstalled the whole thing to see if that's helped. And it did for a bit, o开发者_JAVA技巧nly for the category select box to now be gone again. I can do a QuickEdit and select the categories there, but it's not on the main edit page.

Can anyone help with this?

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While in edit post/page view, check your Screen Options, it's a hanging tab under the header. You may have the "Show categories" checkbox off.

http://codex.wordpress.org/Administration_Panels#Screen_Options