Sharing EVDO via wifi and ICS

I have a Sprint EVDO card connected to one XP machine which connects to the
Internet. I have enabled ICS on this connection. I have also created an
ad-hoc network on this same computer.

On a second computer, I've connected to the first computer via wifi ad-hoc
networking. This second computer shows an Internet Gateway in its Network
Connections. Pinging internet addresses (e.g. ping www.google.com) returns
normal responses (as if this second computer is connected to the Internet).
However, when I launch a browser on this second computer, all web pages time
out.

Also, attempts to ssh from this second computer also fail.

Is there some reason that the ICS seems to be working for the pings but not
web pages?

Thanks,

Ken