I posted this in that forum already and got no responses, but I figured it out! I knew it had to be something specific with this laptop. There are two firewalls; one I knew about and one I didn't. Windows Firewall was the one I knew about and had been tinkering with it since I got the laptop, but there is an AT&T Global Network firewall also that I never knew existed. I disabled that one and enabled the Windows firewall and all is well.