Creating Users Errors

I try to select a category already created by me when I was creating a new user and i can’t see any category on the list. It doesn’t work.
Can you tell me what is the fix for creating users easy and not getting errors about e-mail or can’t see category?
See, I can’t change the categories at all and can’t create new users neither. Please.

This worked for me.
Found the fix. Fix was part of this

in the entry by lodhja
Fix was the following:
line 427 of upload/includes/classes/form.class.php

$field[‘value’] = ‘’;
$field[‘value’] = array();

Made the change to the file and now it is working.