In the case that you are attempting to login to the control panel and get “The password you submitted is invalid”, and reset password is not working, then you can gain access fairly painlessly following these steps.

1) Register a new user on your site.
2) Using a database administration utility, such as phpMyAdmin, go to the exp_members table and locate your new member, then change their group_id for this new account to “1”.

You can now login to the control panel with this new account, and reset your other SuperAdmin’s password and get everything working.