My client, while working on his WP blog yesterday, was doing some cleanup and claims he just removed an unused admin account. The next time he went to login, the login page rejected his account saying "Inactive Account". At this point, he calls me to let me know and I attempt to login as well - now my account says "Inactive Account".
What can cause this and how can it be fixed?

functions.phpif you've written some custom code in there. – dunc Apr 19 '12 at 13:28