Where the heck did my categories, tags, and blogroll go?

Hey,
I posted a new post in a specific category, and I checked the front page of my blog, only to find that the category listed for it was Uncategorized. Then I scrolled down to the tags, and there weren’t any listed. I went to edit that post, and it says there are no categories!

All of the other posts still have their tags and categories intact, but this newest post seemed to mess everything up. My blogroll, categories, and tags no longer exist on the sidebar.

Any ideas how posting a new post could cause a disappearance on such a scale?