Problem "gone away"! I restarted the wifi hub after a bit of a wait so I get a new lease. It now works. Tracert says it was hanging between two cogentco nodes, before dreamhost got hold of it. If you know why, you are probably qualified to steal bitcoins.
Sadly I'd already taken emergency measures with a neighbour's computer, and downloaded the new live installation, and overwrote the old setup. Nothing serious lost except a bit of time.
Thanks for the comments.
