Not logon from active directory

sir!
i have windows 2000 server and active directory my clients are windwos 98, active directory was working properly but suddenly client informed me my password is not correct.error is “the domain passwors you supplied is not correct ,or access to your logon server has been denied”. i changed her password but problem presist, i login from new user and administrator but problem same, i remove active directory and DNS and installed again but problem presist, this problem only founded in windows 98 clients but windows 2000 professional has no problem.
sir please please solve this unbeliveable problem with your great experience.
i m waiting your anserw as soon as possible

thank you