I am of the opinion that communications traffic between the Mac Host and virtualized guest OS' should not occur across the wireless (en1) network. Alternatively, I suggest that HostOS/GuestOS communications be limited to a more hard-wired-centric private network (such as en0). Communications between the private network and the Internet IMNSHO should be supported via NAT bridging between en0 and en1. I have posted a how-to article on setting up three virtualized OpenSolaris 2.1 machines within an Airport Enabled MacBook Pro (10.5.6) using VBox 2.1.4
This article can be found at:
http://fletchermcbeth.wordpress.com/2009/02/19/load-balancing-with-web-server-redundancy-apache/In particular the readers of this thread would be interested in Parts 3 & 4.
Hope this helps.