This past weekend I finally sat down to upgrade my WordPress installation. I was at 2.8.4 and heading for 3.1.2. The automatic upgrader wasn’t working (it would start downloading the zip, and freeze), so I had to upgrade manually. (Using the upgrade instructions here.)
But when the dust settled, my admin dashboard was FUBAR. A number of the blocks on the page weren’t appearing. But the worst of it was that I’d select other pages in the admin and would get a 500 Internal Server Error. Yikes! Interestingly, though, the main site was working just fine.