default gateway

[Guest_imported]

the day bfore it happen i was able to connect to the internet. The next day I couldn't, after checking everyting I found out that my default gateway has not been picking up the default one which we all use. our machines are on static IP's (about 20 of us) and each user are assigned an IP and everyone are using the same gateway. When I activated DHCP my machine picked up a new IP from our server (we have a few that are open) but not the default gateway. This is how we normally set up each machine: "Network neighborhood properties, TCP/IP then assign DNS, disable WINS, Client Network to an NT domain, assign manual IP with proper subnet mask, then default gateway". Before when I do Ipconfig, it would show my static IP plus the default gateway. See now when I view the IPconfig, the default gateway shows the assigned IP on it. example: IP address = 216.56.146.123, subnet 255.255.255.224, default gateway = 216.56.146.123 (instead of the gateway)
I need some help here, I'm not a network guru but i could understand a bit of it.