ICS not working

I've had a small network in my home for two years fairly trouble free. All
boxes are Win98SE with NICs connected to a hub with CAT5E. One has a modem
and ICS installed. The ICS box dials up the ISP and the others simply launch
IE.

Starting last week the clients can not browse, chat or e-mail. Internet
Connection Sharing is loaded on the gateway PC and the modem makes the
connection to the ISP. I have IE on the clients configured to connect
through a LAN. All of the boxes can see each other in network neighborhood
and can share files and printers. But when I launch IE, after a pause, it
comes back with "the page can not be displayed". Only the gateway can get to
the web.

In an attempt to fix this I actually replaced the gateway PC since its only
job is to connect to the ISP. Replacing it didn't make me lose any programs
or data. Are there any typical mistakes that arise when using ICS that may
have gotten me. I thought I configured the gateway the same as when I first
set this up.

Thanks in advance!