Dropped Netware Connections

I am running Novell 4.11 servers, WinNT servers and Win2000 servers. My DHCP is served by a Novell server. Users are running Win2000 Pro at the desktop. Some of my users are on laptops, and when they connect them in the morning to the network, they are unable to attach to the Novell server, therefore they are unable to get an IP address. Occasionally, they will get attached in the morning, and then drop their Netware mapped drives while they are working. After serveral reboots, they are finally able to reconnect. Could this be an issue with the DHCP service running on the Novell server?