All my categories disapeared

I’m running on wordpress 2.3.3.

Old version you’ll say, but I have to stick for it for now.
The thing is, my categories all disapeared.

But when I go to Manage, Categories, and try add them again, it says there are posts under those categories.

For instance, I just added the Music category anew, and it sais “Article: 12″…

But then, the categories are not saved. When I come back in “Manage Categories”, there are still no categories listed. As if they were there, but couldn’t be seen.

Any ideas?

Thanks a lot.