I was having problems with my login in WordPress. The first time everything worked fine, I went in and created a new user with my name (instead of the admin user), loged out as admin and in again as the new user (Eduardo), did my first post and shut down the computer.
Next day I tried to log and get kicked out, tried to regenerate the password and the validation failed. In the end I followed the instructions in the WordPress phpMyAdmin guide and changed the password again. Doing that I realized that the email address of admin and my new account were the same, so I changed them as well.