DHCP server on SBS2003 stops Need assist

sbs 2003
On reboot DHCP works fine. scopes are set so on and so forth.
1 NIC system
after a short bit (20-30 min) DHCP stops and cannot be restarted (error is DCHP had nothing to do blah blah blah)

also get error TCPSVCS memory cannot read error.
Once this happens cannot remotely connect to server.
Reboot and all works fine for the 20-30 min

Also Windows Firewall wont run.
Previously was a 2 NIC setup with ICS but since have changed.