ICS trouble w/2 XP Clients to x64 Vista host net ow works great!

Hello,

Formerly, I had two XPSP2 clients that successfully used a third XPSP2 host to connect to the 'Net.
Host used onboard NIC to the cable modem. Two additional NICs connected the clients to the host.

I installed Vista x64 with the SP1 update on the host PC. After enabling the host to modem connection as shared,
only one client can access the net. Both clients appeared in the connected clients tab to use the shared connection
but only one can be selected.

Both clients can access the host's shared folders, as well as the host can access both client's shared resources.

How can I set up the host and the clients so all three can access the 'Net?

Thanks
TR