USER UNEXPECTEDLY LOGS OFF(Not bychoice)

I have a user that logs into our network. They will be able to use all of the resources they have permission to. However at random times throughout the day they will try to save a file to their home drive on the file server or access another network resource to find that they don’t have access. This is not due to security or logging or locking out they are randomly disconnected from the network. They do have full control rights to everything they try to access. I am running an NT network with windows 95 clients. Any help would be great. Thanks