INternet to SBS server, not to client PC's

I have been given the dubious task of looking after our network, even though I protested I am not experienced enough.  

After an update, our clients have ceased access to the internet.
This sent me into research mode.

We have an SBS 2003 R2 server
2 NIC setup
2Wire modem
Static IP

Here is current  Windows IP Configuration

   Host Name . . . . . . . . . . . . : sbsserver
   Primary Dns Suffix  . . . . . . . : xxxx.local
   Node Type . . . . . . . . . . . . : Unknown
   IP Routing Enabled. . . . . . . . : Yes
   WINS Proxy Enabled. . . . . . . . : Yes
   DNS Suffix Search List. . . . . . : xxxxx.local
                                       gateway.2wire.net

Ethernet adapter External:

   Connection-specific DNS Suffix  . : gateway.2wire.net
   Description . . . . . . . . . . . : Belkin F5D5005 v2000 Gigabit Desktop PCI
Card
   Physical Address. . . . . . . . . : 00-17-3F-9B-E3-03
   DHCP Enabled. . . . . . . . . . . : Yes
   Autoconfiguration Enabled . . . . : Yes
   IP Address. . . . . . . . . . . . : 203.45.57.224
   Subnet Mask . . . . . . . . . . . : 255.255.255.192
   Default Gateway . . . . . . . . . : 203.45.57.223
   DHCP Server . . . . . . . . . . . : 10.0.0.138
   DNS Servers . . . . . . . . . . . : 10.0.0.138
   NetBIOS over Tcpip. . . . . . . . : Disabled
   Lease Obtained. . . . . . . . . . : Thursday, 5 November 2009 2:43:18 PM
   Lease Expires . . . . . . . . . . : Thursday, 5 November 2009 2:53:18 PM

Ethernet adapter Internal:

   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Broadcom NetXtreme Gigabit Ethernet
   Physical Address. . . . . . . . . : 00-1A-64-AB-AA-68
   DHCP Enabled. . . . . . . . . . . : No
   IP Address. . . . . . . . . . . . : 192.168.16.2
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . :
   DNS Servers . . . . . . . . . . . : 192.168.16.2
   Primary WINS Server . . . . . . . : 192.168.16.2

C:\Documents and Settings\Administrator>ipconfig

Windows IP Configuration


Ethernet adapter External:

   Connection-specific DNS Suffix  . :
   IP Address. . . . . . . . . . . . : 203.45.57.224
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : 203.45.57.1

Ethernet adapter Internal:

   Connection-specific DNS Suffix  . :
   IP Address. . . . . . . . . . . . : 192.168.16.2
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . :

I have run CIEW again, however this has not fixed the issue.
I have also noted that DHCP is running on the server and DHCP is also running on the router.
I also understand that this is not hte ideal (or supported) setup in that the router is sitting outside of the external NIC, rather than inbetween the external and the internal.
I will look at changing this afterward, but obviously need to get internet back up and running on the clients.

Clients have full access to the LAN.
Clients cannot ping an IP address, but can ping the server.
Server has full access to the internet.

I ran NETDIAG but don't know where to get the results.. lol

Any help or pointers in the right direciton would be appreciated.

I ran