Small Business Server ping through

Hi everyone,

I have an SBS 2000 server with two NICs. One IP is 192.168.0.1 which connects to the LAN. The other is 192.168.1.1 which connects to a router and the internet.
I can ping the internet OK from the server and can access the internet via clients on the LAN using the SBS ISA proxy.
I can ping the 192.168.1.1 from the clients but I can not ping the internet from client PCs.
Does anyone know if it is an IAS setting, or some any other setting which may be prohibiting pings via the SBS server.

regards
Marty