*** Improved by Wrobinson on 12/22/07 ***
You need to configure DHCP to include a default gateway of 192.168.10.1 for the workstations and enable routing on the server for network traffic from the internal network to be forwarded to the external gateway and out to the Internet. Chances are that you will have to also setup a static route of 0.0.0.0 to the external gateway.
*** End update ***
I may be wrong on this, but if your internal NIC receives a request for something not 192.168, etc related, it would send that request to the gateway, which you do not have configured on the NIC.
try configuring the gateway