Domain Client Pcs Can't Access The Internet

[MFaklis]

I have (had) a working Windows Server 2008 domain server, until I had to replace the motherboard. The domain server is the gateway between the Intranet and the Internet. All client computers can still see the Intranet, but they lost access to the Internet. The client computers are able to find ip addresses via nslookup to the DNS running on the domain server, they just can't see beyond the domain server to the Internet. The domain server has full access to the Internet and Intranet.

I've been researching this and ran into a brick wall where I'm out of ideas. Can anyone give me a clue?