DHCP and Win 95 with Win 2000

At our school, we have a problem with Win 95 machine not being able to register with DHCP and is not abtaining an address that is valid on the network. When a user tries to log on they get a message that states that the user name or password is notvalid when indeed it is. If you log on locally, then do the winipcfg from command and release and renew (it gets all the same info it had before releasing) and reboot, you get on the network with no problem. Can some one please help out???