How do Site Admins Add Users with Pro Sites?

In the Wordpress Network Admin, I have the box checked for:
• Both sites and user accounts can be registered and
• Allow site Administrators to add new users to their site via the "Users –> Add New" page.

However, when the Site Admin and Network Admin go to add a New User, the page blinks and nothing happens. No user is created and the information inputted is still sitting there.

This also occurs in the Network Admin under Users –> "Add New".

Currently, the only way to add a New User to the network or sub-site is to do so Manually via phpMyAdmin.

I'm assuming there is some kind of conflicts going on with the User Roles, but cannot seem to track it down. ...also, there is no record posted to the debug.log regarding the attempts to add a new user.

Note: Before, when I was having trouble with Pro Sites billing/site cancellation, Umesh was able to create his own account. However, now this action is broken.

Thoughts? ..(support access has been enabled)