Windows PC join Active Directory Error - The Specified server cannot perform the requested operation

Error occured when make Windows PC join Active Directory with message "The Specified server cannot perform the requested operation."

Case 1

http://www.computing.net/answers/windows-2003/problems-joining-a-domian/5058.html

I've setup a Active Directory and a DNS Server on Windows 2003 Enterprise server. First i could join my xp pro workstations to my domain fine but i couldn't log on with my domain user accounts from the workstation. i would recieve the following message:
"The system cannot log you on because the domain home.ics is not available"
i can ping the workstation from the server and vice versa with ease. i can also browse shard drives and folders easily when the xp pro machine is on the workgroup. then i looked at this artcal and took the last guy's advice:
http://computing.net/windows2003/wwwboard/forum/4635.html
This totaly screwed everything up. Now when I try to change the system settings on the XP workstations to join my domain, i receive the following error:
'The specified server cannot perform the requested operation'.
i can look under the active directory on my DC and i see the workstation's account is disabled for some reason. I've tried to enable the account and re-join the domain from the workstation just to get the same results. 'The specified server cannot perform the requested operation'.
i've also tried to rename the workstation and rejoin the domain. same results.
This is extreamly frustrating to me and i dont know what else to do. any words of wisdom would be greatly appreciated, thanks in advance.

Case 2

http://adirectory.blog.com/2012/06/specified-server-cannot-perform-requested-operation/

http://support.microsoft.com/kb/2018583