Zone Alarm Pro and Internet Connection Sharing

Had same problem. This (from ZA help) worked for me.

Select Firewall|Main.

Click Advanced.

In the Internet Connection Sharing area, choose your security settings.

Select the 3rd option:

This computer is an ICS/NAT gateway Zone Labs security software
automatically detects the IP address of the ICS gateway and displays it
in the Local Address field.

You also can type the IP address into the Gateway address field. (I
DIDN'T)


Selecting Suppress alerts locally if forwarded to clients, will suppress
alerts forwarded from the gateway to clients to also be displayed on the
gateway.

Click OK.