W98 PC fails to locate DHCP IP Address

I know this has been ased quite often by others but i still have no rsolution to the problem. I currently has an NT network with 48 WIN98 client machines. I can originally set up the clients to function under DHCP but after a period of time many clients start to drop off the network and will not renew their addresses. If i assign a static ip sddress the clients log on fine. Is this a WIN98 feature(sarcasm)????? Please help.