Upgraded; can’t create new categories or delete old pages

I re-installed and upgraded WordPress — 2.1.something. . . how do I determine the exact version?

I cannot create new categories or delete old pages.
When I try to create a new category, the form fields clear and nothing else happens.
When I try to delete old pages, they appear to delete, but when I go back in to check on them, they are still there. And they’re still there on the site.

I’m working out of Safari and have tried emptying my cache and reloading.

This seems to be a common problem. I can’t find any solutions in the posts I’ve read, however, so I’m hoping that someone will be able to help. Someone suggested that it might be because the upgrade failed to completely install and offered a link to a forced upgrade script, but it was for an older version.