Error while trying to access Active Directory

I would like to import some users and add it to the list of my directory when I am prompted to an error message saying: “Error while trying to access Active Directory.”
I tried to give a code (Forms/SysUserADUserImportWizard/searchADUser) and I saw that the Active Directory searcher broke into this line:searchResultCollection = directorySearcher.FindAll()”. I got this error after using the Microsoft Dynamics AX 2009 Active Directory Import Wizard. Do you have any idea what might be the cause of getting the error?
Any help from you guys is greatly appreciated.

