I don´t know Norton 360 very well, but it caused some trouble in the past.
Please make sure that you configure your windows firewall via the advanced manager and disable N360 firewall.
http://www.howtogeek.com/112564/how-to-create-
advanced-firewall-rules-in-the-windows-firewall/
Another problem could be an old OR a new ethernetdriver. If you´ve used the default windows update, you may have gotten a faulty new driver. In that case go to driversettings and restore the old one. Check the ethernet-cards properties also if you have some ah... "Windows Optimizer" Software installed.