wp-signup.php Re-directing to home page and NOT Pro Site Registration page

Hello once again.

Fantastic support here, much appreciated.

Here is a bizarre issue we've encountered while trying to implement Pro Sites into our current WPMU / BP installation.

When a user registers fresh, they can create a Pro Site with no issues.

However, when a already existing user tries to create a Pro Site (by accessing mysite.com/wp-signup.php) they are not taken to a page to get their Pro Site, instead they are re-routed to our home page (mysite.com)

Very bizarre issue. Does anyone have any idea as to why our signed in users are not able to activate their Pro Sites?

I should also mention that NON registered users who manually enter mysite.com/wp-signup.php are redirected to mysite.com