When clicking on the modal popup, a class usually gets assigned to the modal element. Since the class is missing, the styling associated with that class is not loaded. This usually is from either 2 bootstrap javascript or 2 jquery files being loaded on the page. You can turn off the two settings I mentioned if there was no change.
In the meantime while we need to narrow down what's causing the conflict, in your SCLogin theme, can you try changing:
In media/sourcecoast/themes/sclogin/default.css around line 24
div.sclogin-modal.modal.in {
to
div.sclogin-modal.modal.in,div.sclogin-modal.modal.show {
When I get the email/username, I can look at the JFBC/SCLogin settings further.