Windows 98 SE/Netware 5.1

I have about 20 Windows 98 SE clients that have Netware Client 3.3 installed. Their preffered server is set to the 5.1 server. They map two drives off to shares on an NT box. When they click on the shortcut they’ve created to one/both of the shares,the PC’s are locking up. At this point I have blown a few of them clean and reinstalled WIN 98 to encounter the same problem. H/W consists of an Intel Pro 100+ management NIC,ATI Rage Pro
card,Sound Blaster PCI(on board). Any ideas of what could cause this freezing? I have also updated to all current drivers. Seems to between NT server and the 5.1 server.