No permission to access resource

We have a Red Hat box running Samba and this Red Hat box shows in Network Neighborhood. Sometimes when a PC tries to access that Samba directory, a message stating there is ‘No permission to access resource’ pops up. After that, the rest of the PC’son the network disappear and only the Samba directory is viewable. If you reboot the PC, the rest of the PC’s appear on the network and you can access the Samba directory with no problems. How can I keep that error from happening, and does anyone have any idea why the rest of the PC’s (Win98) disappear from the Network Neighborhood?