Anyone experiencing problems with categories today?

Using 2.9.2. After installing, my dashboard says there is 1 category, i.e. “Uncategorized”. When I go to Post > Categories – “Uncategorized” is not listed. Odd.

Then I try to add some categories of my own. They appear to be saved but when I leave the page and return – all the categories are gone. When I try to re-add them I get an error message saying “The category you are trying to add already exists”.

I’ve installed and used WP many times without any problem. First time I’ve seen this. I’ve reinstalled WP about five times, dropped the database – but the problem is still there.

I may be paranoid but wonder if a suspect theme I installed and then removed could be responsible for this? Every seemed OK earlier today.