Disappearing directories in Win98

System is running Win98, 2ed with Novell Client 3.3. Network is NetWare 5.1 with 2 servers. BorderManager 3.5 is used for Internet access. At times when navigating to the BorderManager server to view files/directories, those in the second volume (labeled VOL1) are not listed. Even mapping drive letter to this volume doesn’t work. Are visible from other systems running same Windows and client versions. At other times, files/directories are available with no problem. No pattern detectible to when they are visible and when not. Only happens on this one system. Is this a registry issue?