Please check this thread:
http://www.gnutellaforums.com/help-s...tml#post303417
It has the current (simple) solution for getting Phex to work properly in a LAN.
The problem is the firewall detection algorithm - Phex sees the private (LAN) address but didn't ever connect to a non-private address so it thinks itself firewalled and a private address in another network would be unreachable.