BuddyPress.org

@David, possible you can check to see if you have any errors in your server logs? All that’s happening is a pretty simple AJAX request, not any different than loading any other normal page only it happens underneath it all.

If there’s a server error or some kind of authentication that it’s waiting to get back, that would be my only real guess?

Also, you could try to use Firefox and install Firebug and YSlow. YSlow can help you determine which HTTP requests are slow and track down what particular PHP file is causing the bottleneck.