gurney:
I tried on your site without issue using Firefox. Can you be more specific of browser version your using or any other variables that might be of note to help us test? I also noticed that you don't have a redirect set up for your non-www version of your site. That will definitely cause you issues as you move forward.
Cross-Domain Receiver / www redirects
Login = Community Builder
Upgraded to IE 8.0 (same issue)
When logging on using facebook:
popup refreshes, but login appears unsuccessful. If you manually refresh, you are logged on in pop-up, but original window does not refresh, or log on. The pop-ip should go away, then refresh the original window correct?
The subdirectory thing shouldn't be an issue, we've tested that quite a bit before. You do want to make sure that the callback URLs in your FB application include the subdirectory name.
The (missing) .htaccess file wouldn't be causing this issue, but it could cause you other issues once we get past this one.