The virtual url call is incorrect. the main page calls http://yourdomain/installfolder/activity/feed and does not work. On my site the feeds work on the profile page and any member page but not the site feed.
If you call this url directly and get the feed; http://yourdomain/installfolder/buddypress/activity/feed
then changing the call will fix it. I will be back with that solution as soon as I have it.