Can’t use port 110 on Win XP

Here’s my scenario. Have custemer with two computer behing a linksys firewall. He uses earthlinks pop email server. He runs both norton personal firewall and zone alarm to protect his PC (he’s had problems). One of his machines has not problems accessing the server. The other is unable to. We have brough a laptop to his site and have no problems retrieving the mail. We have also reset the router and verified that there is nothing blocking the port at the server. We are unable to telnet to port 110 from that machine either (we were able to from the others). We have shut down both firewalls also with no luck. Any ideas?