Unable to ping outside network

Hi,
I have a windows nt4.0 network. I have a windows 2000 server as our DNS.I’m unable to ping outside the network whether by name or ip address example: www.aol.com. What would be the reason that I would not be able to do this? I can however ping w/no problem from the server that the users connect to, to get to the internet
I do have internet access and I have no problem w/that. Internally I can ping by name and by ip address.
Any help would be appreciated.