I have had some strange problems having a Multihomed win XP machine on a small Win XP LAN. Multihomed machine is connected to a wireless LAN and also has a RICOH multifunction connected to its LAN port(having a different network address). After the LAN was setup this way, it would stop working after a few hours. An article on the Internet suggested that the browser service should be stopped on the Multihomed PC. I turned it of on all the 4 computers on the LAN. The network would keep functioning for a few days before it stopped responding. The Computers would show as being connected, but could not access the shared docs on the Multihomed PC or print to the Multifunction attached to it, or access the Internet.
In response to a second posting on the Internet, it was suggested to disable NETBIOS over TCP/IP on the Multihomed's LAN port connection(one with the Multifuntion). I implemented that and the network has been working fine for 2 days.