Last week I upgraded a client's WordPress site from 2.8.2 to 3.2.1 (long time coming). When I did the upgrade, I remained in the Dashboard, fixing up things and doing stuff, no problem.
Today, I find out that cannot log in. The login page refreshes if the password is correct, shows an error if the password is wrong.
Things I've tried that have NOT worked:
* removing/renaming the plugins folder
* clearing cookies
* force-upgrading the database
* turning on WP_DEBUG
* replacing wp-login.php
* upgrading wp-config.php
* resetting my password manually through phpmyadmin
I've searched on the forums and the internet and have found no other ideas. The only funky fact I noticed is that the server is running PHP 5.2.1 and WordPress's minimum requirements are for PHP 5.2.4. I doubt that could be the source of the problem since the difference isn't so great. But maybe not?