Right. I recently upgraded this installation of WordPress to 2.6, and just now tried to login as admin to change some settings. Nope, kept looping me back to the admin login page. Yes, I was using the correct password.
Turns out I was having a conflict with older plugins (I hadn’t disabled them). So, I went in to the backend MySQL database (via phpMyAdmin), and edited the wp_options table. I changed the option_value for the row with “active_plugins” to
a:0:{}
which basically turned off all plugins. I could then login (and turn on plugins one at a time to find the culprit).
Note that you can also change your password via the backend by editing the wp_users table and using the MD5 function on the password value. Neat.
