Passing traffic from 2 different networks

Greetings,

My situation is as follows:

Site to Site VPN using 2 Linksys VPN Routers.  One router located in a
remote office, the other sitting on a DMZ off of my ISA server.  The
tunnel is established and working.  Clients in the remote office network
can talk with the DMZ clients and vice-versa.  Now my challenge is to
get the traffic from the internal network, behind the isa, to talk to
the remote office clients and to get the clients in the remote office to
talk to the network clients behind the isa.

From the ISA server I can ping the remote network clients.  What do I
need to add to the ISA to allow the clients behind it to communicate
through the ISA and to the linksys sitting on the dmz and then out to
the remote network?

The remote network has an IP subnet of 10.116.1.0 - Internal IP of
Linksys is 10.116.1.1
The ISA DMZ is a 10.112.1.0 network - Linksys DMZ address is 10.112.1.3 
The Internal network behind the ISA is 10.128.0.0 -  ISA internal
address is 10.128.3.4

On the ISA I have a route stating that any traffic destined for
10.116.1.0 mask 255.255.255.0 use 10.112.1.3 as the gateway.

From a client behind the ISA I have a static route stating that any
traffic destined for 10.116.1.0 mask 255.255.255.0 use 10.128.3.4 as the
gateway.

When I ping the remote subnet frm a client behind the ISA my requests
time out.  The same happens when I try to ping a client behind the ISA
from a client on the remote network.
So I'm assuming that the ISA is not allowing this traffic.  How can I
tell the ISA to allow the traffic?

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