markwelch - 7:51 pm on Jan 12, 2009 (gmt 0)
I finally posted this message after many days of struggling, and I expected many more days of confusion from this problem. But today the Comcast technician solved the problem. He was equally baffled by the strange collection of symptoms, and replicated the problem on his own laptop. Although it didn't seem likely to fix the problem, he went ahead and replaced the gateway with a modem/router combo -- and we could immediately access the site.