From that same file:
RESTORE ADMINISTRATOR PERMISSIONS
So, you've messed with the Role Manager (or some database properties) and you've locked yourself out of WordPress... Well done!
Follow these instructions to get yourself back into the system:
1. Edit this file and change the value for $adminuser that appears just below these instructions. Set $adminuser equal to your admin's username. Save it.
2. Upload this file to your WordPress directory as "restore-admin.php". It should be in the same directory as your wp-config.php file.
3. Access this file from your web browser using the URL similar to http://example.com/restore-admin.php . You should be redirected to a login page or a profile page. Login as the specified user and verify on the login page that the additional capability "edit_users" is now set.
4. The user you have specified should now have edit_users permissions, and should be able to change user permissions as necessary to restore any required access. Note that this DOES NOT restore edit_users permission to a ROLE, only to the user specified below. To restore edit_users permission to a Role, use the Role Manager plugin.
5. Optionally delete this file. Although this file will only ever add edit_users capabilties to a single user as hardcoded in the file, it seems safer not to tempt fate by leaving it around for hackers to attempt to tamper with it.
I dunno... But heck, what do you have to lose at this point ;-)