It occurred after I install the plugin More Fields, add fields to more friendly instead of using custom fields. I created a box, it worked perfectly. On the page add new post, I was better placed than the box created by the plugin, below the category box.
Then I realized that the box to select the category of the post disappeared! Ja deactivated all plugins, I activated, I changed the theme, and the box does not come back! Really disappeared from my user (admin).
Logging in as another user, the box is there but not as admin.
Strange, is not it?
How do you solve this problem!