Could not Log on

Hi,

We have one Windows NT Server and 8 Windows 98 SE Systems.The Staff log on from Win98 using User-Level Access Control which the NT Server Authenticates the Users.All was working fine till April 17.But on 18 April the NT Server was not allowing any Users to log on.Even the NT Server was not logging on despite the fact the Username & password was correct.

We usually never set password for NT since it is a 24hr Company and we work in shift.But today morning it was not allowing to log on and looks like somebody had changed the password.

After some hard time we were able to log on with a password which we typed by guess.

Any Solution would be welcome.