1and1 first told me that they could access the site, so must be my ISP
Cox Cable said they could access it, must be my computer or router. Bypassing the router did access it, but I won't run that way.
I researched such blockage, totally reset the router to an older config, changed DNS's, etc. etc.
After 4 hours of fruitless troubleshooting, I concluded that in fact the server was denying me access.
Back to 1and1, and THEN they confirmed that an (automatic, camera) ftp login error had caused my IP address to be blocked!
Grrrr