Resource Sharing in mixed environment

I am running a NetWare 5.1 network with Windows 2000 and Windows 9x clients. If I want to share a resource from a Windows 2000 professional client (ie. printer), I can connect to it if I use another Windows 2000 computer. If I try to connect to it with a Windows 98 client, I get the following prompt: “You must supply a password to make this connection:
Resource: \\\IPC$” I try to enter as many passwords as I know, but it doesn’t work. The weird thing is that I was able to connect to it once from a Windows 9x machine, but for some odd reason I lost that capability now. Please help.