Network connections drop out

Have a WinNT network with 2 servers. 1 Domain Controler 2nd File Server. Problem whenever a PC restarts network connections drop out. Is problem with browser service? Have turned LMAnnounce switch on 98 box’s off and have disabled the browse master key on NT workstations. Servers are set so domain controller has Master Browser set to “True” and maintain server list set to “yes” in the registry. What is missing?