Error 15401: ... 'username' not found. Check the name again.

Hi everyone,

I recently installed a SQL server 2000 Standard Edition in a Windows server 2003 operating system. This SQL server is connected to a logon server (Server 2003 Active directory) with a domain name of 'EternalPlansInc'. When I try to add a username for the SQL server, windows authentication, this error occur:

Error 15401: Windows NT user or group 'EternalPlansInc\junn' not found. Check the name again.

I can't figure out how this happen although the username junn can be viewed from the SQL New Login form... and by the way the SQL server is already joined in the domain 'EternalPlansInc'.

What should I do... I'm stock with this problem for almost a week....

Please help with this one.... Thanks in advance...