If you have LW running on two accounts
at the same time they have to use different ports. They both can't use the same one. LW will choose a different port automatically when you start the second one. Where you might run into problems is if you haven't made exceptions for the other port through your firewall and router. It might connect on one account and not the other.
Directions to port forward your router:
Port Forwarding for the Thomson/Alcatel SpeedTouch 530
Hope this helps
.