There was some sort of problem where the sign up would add a new user, but the password would be the cpanel password
so I changed the names of the variables defining the cpanel passwords to have auth_ before them. e.g. $auth_username $auth_password, and changed the according references where it sends those credentials to log into the cpanel, and it adds pops fine now.
I changed a lot of the code though (so much that it's almost a completely different hack

), so I probably can't give accurate line numbers for everyone else to change their copies. I just know that in the hack attached in the first post of this thread, the file to look in is neowebcreate.php.