The user does not exist or is not unique

Apr 23, 2009 at 7:59 PM
Please tell me someone else knows what to do about this.  I don't believe it is a SharePoint issue any longer, but I don't know how to resolve this.  I have MOSS 2007 installed on one box with SQL Server on the same one.  I use AD authentication, and I have allowed all authenticated users to access this portal.  Upon hitting the site, 99% of the people have no issues.  I have 4 people who get the error, "The user does not exist or is not unique."  Anyone have a clue as to how I figure out what is really going on?  One of these guys uses a thin-client workstation with XP and IE 7.  One uses a regular desktop XP and IE 6.  The other two use regular desktops with Vista and IE 7.  I have checked the AD, and everyone looks to be set up properly.  I just built the site, so there are no workflows.  We didn't migrate from another SharePoint or anything.  It is just a quick load and launch really.