Username/Email Already in Use

We do not use the built in AJAX setting for Community Builder as there were issues with using that, so turning it off in CB does not turn off our AJAX checking.

If you can provide the site name, we can look into the response the AJAX is returning and try to determine a cause for the constant rejection.

I could swear I posted this earlier, but it's not showing now

The issue doesn't have to do with your SEF or anything, it's actually with that GoDaddy banner at the top. We make an AJAX call to our component to return a '1' or '0' (true or false) if the username or email is available. Unfortunately, that banner is being inserted into any pages that are returned, so it's not returning what we're expecting. You can see for yourself by using the following link:
<!-- m --><a class="postlink" href="www.industrythoughts.com/?option=com_jfb...le&username=testname">www.industrythoughts.com/?option ... e=testname

You can see the GoDaddy banner with a '1' at the bottom indicating the name is available. However, our code is reading all the other gobbledy-gook and seeing it as a 'false'. If you can, I would highly suggest disabling that banner if at all possible as that will cause havoc with any AJAXy features in any components. If that's not possilble, you can remove the two 'onblur' lines on the username and password fields in the following files. That will remove the ajax functionality:
componentscom_jfbconnectcomponentviewsloginregistertmpldefault.php

Good luck.