Win2K and Broadband connections

Ok, I just tried setting up my new laptop on my cable modem. I called AT&T and had the MAC address of the NIC provisioned on the network, and I am able to renew the correct IP address using “IPCONFIG/renew” at the command line. The problem is that after the NIC gets this address, that is it. I cannont PING out to anywhere on the net, nor can I ping back to my computer from another on the net. I checked my event logs and I get the following errors:

1) The IP address lease “” for the Network Card with network address “Mac address here” has been denied by the DHCP server “IP”(The DHCP Server sent a DHCPNACK message)

2) Your computer was not able to renew its address from the network(from the DHCP Server)for the Network Card with the address “MAC address here”. The following error occured” The semaphore timeout period has expired. Your computer will continue to try and obtain an address on its own from the network address(DHCP) server.

I had called AT&T’s tech support and finally after the fith time calling, the girl got an attitude and told me the problem is not on their end, their is nothing else they can do. This is the first time I have tried a Win2K machine on this connection. The laptop connects fine withother computers, and I have even tried to update the drivers for the card. Does anyone have a clue??? Should I re-format this thing and put Win98 on it and see what happens??? Any suggestions at this point would help.
Thanks, PC