Intermittent Disconnects

This has been driving us crazy for several weeks. We have a user, NT 4.0 connecting to a 4.0 Domain with several servers. Periodically throughout the day she will lose connection to one or more servers. We have tried everything we can think of, changed all cables, moved to a different port in the office as well as a different port on the switch, changed NICs, changed PC completely. Nothing has helped. She’ll call us about a problem, can’t log on to SAP, not getting mail, not able to print. Thenmaybe a half hour later she will call back and say it is now working. This happens two or three times during the day.

Any help would be appreciated.