DHCP Clients not logging onto domain.

I have a growing problem where new 95/98 DHCP clients, when booted, do not prompt for the Network Logon. If I Log off then log back on, or if I use “Release All” then “Refresh All” in WINIPCFG, it works correctly. I have recently created a new PDC running DHCP to resolve this to no avail. PLEASE HELP!