I use a router but only one computer uses LW (port forwarded to do so.) No firewalls here. Which might spell a small part of the difference. I don't know. I suppose I should mention the vpc win 2k but it can't receive incoming anyway. I don't think I can fix that. Not whilst it's coming from the same computer. A bit more complicated. But at least I only use it for testing, & similar, etc.
By the way I have my ip on my LW for DC so there's no firewall concerns. Same as the winn 2k.