TCP/IP Help Needed – Desperate

I have two NIC’s on my server, one for LAN and one for ADSL connection, my problem is:-
my server(IP 10.0.x.x sub 255.255.255.0 no default gateway) can ping the ADSL(IP 217.40.x.x Sub 255.255.255.248 GW 217.40.x.x) and my server can ping any client(IP 10.0.x.x sub 255.255.255.0),my clients can ping the server but not the ADSL, what is going wrong please???