Upgrade won’t run — database error

I try to log in to my dashboard, and it says that WordPress is out of date and I need to upgrade (to 2.3.3 I guess). So I click on the link. It says it’s going to take some time, but after a minute or so it stops and gives me this message:

WordPress database error: [Unknown column ‘user_nickname’ in ‘field list’]
SELECT ID, user_nickname, user_nicename FROM wp_users