Bug when new user attempts to checkout/register new username that is in use

[jermo5]

Running:
Joomla 2.5.4
JoomlaLMS 1.2.5
VM 2.0.10

When a new user adds a product to their cart and tries to check out (we have "registration required upon checkout" enabled) with a new username/password... if the user just so happens to type in a username that already exists in our system, no error is displayed, but instead redirects the user to a slightly different formatted registration page and this loops over and over with no error message ever displayed.

Is there a way to tell the user that the username is already in use and to pick a new username?

Thanks!

Jeremy
site: www.agility-u.com