This happened to me yesterday, and you cannot just 'reset' your password cause of the encryption in phpmyadmin.
Login to phpmyadmin, select your database, go to SQL And enter this.
Code:
UPDATE `wp_users` SET `user_pass` = MD5( 'new_password_here' ) WHERE `wp_users`.`user_login` = "admin_username";
"new_password_here" - replace this with the new password you wish to use.
"admin_username" - replace this with the username the password should be updated for.
Then just login with your new password.
http://kb.siteground.com/article/How..._password.html