Can not log on to Domain

WINDOWS98SE can not log on to WINDOWS 2000 DOMAIN CONTROLLER
My server is a Windows 2000 Advance Service SP2, configured as Domain Controller.
Prior to this, everything was fine. Windows 2000 Professional was the OS of my workstations.
Then a new PC came with a Windows98SE OS. I thought it was going to be easy adding it to the network but I spent some time on it and I was not able to log on in our domain.

When the Win98 prompts for the Log on dialog box (username, password and the Domain). I typed the appropiate username and its corresponding password but failed. I used the administrator account and still failure. Do you have any idea resolving this problem?

YOur advice to this matter is highly appreciated.