hey there tooney
well first off when you share connection ....internet connection sharing ..it usually turns a firewall on ... have you turned the firewall of ? do you get same result ..also do u have any other firewall programs ?
Also in your router ..you didnt specify model but is there firewall program built in ..
also do u have to open your ports for firewall or does your router do that for ya
well those are some starting points ..
but just hook one pc up to the asdl and if you can ftp then it is in your router ...or hook both up then you know for sure it is in your router
also check and make sure your not dmz host ... it will open all ports but other machine it will block ...