You stated at the beginning that problems started after installing Norton AV. Check your norton options to make sure there's no way LW is restricted in any way. Also make sure there's not firewall also. If there is then you'll need to decide between Norton FW & McAffee FW. XP firewall should be off!!!

Norton AV might slow down verification of downlds but shouldn't affect actual downld speeds! Contol-Alt-Del & see what apps are running. See if there's more than one Norton activity.

BTW double-check your mcafee settings. Make sure any port settings in your FW match those in your LW program under LW's menu, Tools>Options>Advanced>Firewalls