Vpn will not allow access to server's local subnet

[prldoyle]

I have set up a site to site VPN and it connects and traffic is routed correctly over the vpn.

Remote clients can ping all devices on the server's local subnet but have not access to services (remote desktop, dhcp, etc.) however remote clients can use services through the vpn to other subnets not local to the vpns server, please see this diagram (http://www.dd-wrt.com/phpBB2/files/drawing1_111.png) to help explain to this. for example i can connect (from the remote client and dd-wrt router) and use the voip service from the voip server on the 172.16.2.x subnet and also connect to a LAMP server on a client pc. but can not ssh, telnet or even receive DNS from anything on the 172.16.1.x subnet. (except 172.16.1.51, the open vpn server which i can ssh to and web browse through the vpn)

The router is a DD-WRT server acting as a openvpn client and the server is an openvpn access server.

I have gone for routing over the vpn instead of NAT as alot of voip services doesn't work once NATed.

Some one has suggested firewalls, however, The firewall which is doing port forwarding has rules saying allow all traffic between the 172.16.x.x subnets and 172.18.x.x subnets, and this must be working as traffic between those subnets must go via this firewall and they work.

The subnet which is having the problems doesn't route traffic via the firewall (as the vpn server is on the same subnet, so traffic will go directly between server and vpn-server) so it must be a firewall on either the dd-wrt router or openvpn server? (the SPI firewall on the dd-wrt router is set to off via the gui) I am new to both of these technologies, any suggestions how i check or add rules to make sure that neither is blocking anything from traveling through the vpn?