From that same file:
RESTORE ADMINISTRATOR PERMISSIONS
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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 ;-)