Problem connecting networks via VPN

Hello,

I have a problem connection the network at work to my home network.
Since I'am still very new to Linux I'm not even sure I want to do is
possible:

At home I have a Router (NETGEAR WGR614) with a broadband connection.
Then I have a small Linux server where I installed vpnc. I can also
connect to the VPN server at work and then access all other computer
at work behind the VPN server without any problems. But only from my
linux server where I run the VPN client.

I enabled the ip_forward on the Linux server and have there a DNS and
DHCP server installed, setting the standard gateway and DNS server to
the Linux box (which has the Netgear router as standard gateway).

>From my Windows box I can connect to the Internet using the Linux box
as gateway, so the ip_forward works, but I cannot connect to any
computer at work. It looks like the Linux box doesn't allow the IP
forward to use tun0 interface. Do I have to add to allow this? Or do I
miss something?

Thanks,

Thomas