So you can browse the windows computer. I didn't think you could earlier. So with your browsers from each computer go to http://www.whatismyip.com/ & tell us if the ip's are the same. If not then that's the ip you should use to DC. I'm thinking you might need to set up a different listening port for one of the computers. Say one uses port 6346 & the other 6348 or 6342 etc. You can set that in Tools>Options>Advanced>Port/Firewall settings or mac that's LW Prefs of course instead of Tools.