Problem With NAT

Problem: Completely windows platform n/w setup; no domain environment. Configured NAT & DNS (std primary) on same win2k server (no DHCP, have multiple Public IP’s). Configured DNS forwarder to resolve externalsites. Setup works fine for an hour or so then complaints in that mials are not working, some times sites are not opening. But as soon I restart the routing n remote access services all works fine. Have to restart the services every hour or so. VERY URGENT, IMPLEMENTATION ON STANDBY.Please give me a solution.