Butrfly--I had installed Stopzilla firewall, bug and virus catcher, which turned out to be part of the problem. When I installed it, I uninstalled the other firewalls etc., but the Comcast guy said that once in, they can never completely be removed.
Stopzilla and the remnants of the other firewalls apparently became so enmeshed that they brought everything to a halt. Part of the problem is that my pc is old. Dys also has Stopzilla, but has had no problems at all.
My lesson for the day: Just stick with the free McAfee firewall provided by Comcast and don't add anything else. What a huge mess!
This is one of the few times I've seen Dys stumped. He is usually patient, taking things apart and putting them back together without ever getting impatient. He just keeps going until whatevery it is is fixed. He still didn't start throwing things the way some many people do, but, even though he came close to figuring it out, this is one of the few that had him stumped.