computers don’t apear in Ntwrk Nbrhood

I have a Novell netware network running Netware version 3.12. All the workstations are windows98. When I go to network nieghborhood on some of the computers, there are 2 computers that don’t show up in the list. Even if I try mapping a network drive, it won’t work, it gives me a message that the computer is not found. But I know that the computer is connecting to the network, because it can access the server, so there’s nothing wrong with the computer hardware. Would you have any idea why this is happening and what I can do to correct it?

Thank you!