I came across another lengthy discussion on this subject:
http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/99558
It appears some work has been done to correct this problem but if I understand the discussion correctly it still is not resolved, at least at the timeframe of this thread.
In our case, we have systems with no IP identity of any kind--no IP address and no gateway, and they are connected by switches. There is no router in the network. They receive IP addresses through this special service that we've written that runs on one of the systems. All communication is done through limited broadcast. This works fine one our Linux and Windows boxes but not FreeBSD.
It may very well be user error in our FreeBSD code. Has anyone managed to get limited broadcast to work under FreeBSD?