LW cannot connect using same connection or listening ports as other LW's on same LAN. Try changing the connection & listening ports, even if manually if necessary. Ports to try are 49152 - 65535 (64049 is a good one to try.) Routers tend to reserve ports for particular programs on each computer. So the 3rd LW "might" be clashing with the port from one of the others. Something to try anyway.

Go to LW's menu bar, Tools -> Options -> Advanced -> Firewalls & check listening & connection ports.

Something else to try is disabling all options in the Performance tab section; a description is 3rd on list here: http://www.gnutellaforums.com/connec...t-connect.html