Network slowdown and strangeness

2 Windows 2000 Pro workstations, 11 Windows 98 SE workstations, 1 NT 4.0 server. Recently all machines in the office with exception to the W2K and 1 Windows 98 machine lost access to open files on the server. The working machines were on separate hubs. All machines could see files on the server, but some could not open them. The files in questions were Office 2000 documents and spreadsheets. These files would open on the local machines sporadically. All machines were able to access the Exchange. Noticed several new files loading when checkin msconfig. Especially bymer.scanner loading in the Wininit.exe. Any ideas?