[otrs] missing customer user

We've recently upgraded to OTRS version 2.3.4  Our (internal) users login at customer.pl and are able to authenticate against Active Directory.  The problem is that there are several new users that were added to the Active Directory after the initial sync to OTRS.  These users can login successfully and I can find them if I search in Customer Users.  But for some reason, I don't see them in the list when I click Customer User <-> Groups so that I can add them to a group.  I've tried running the sync- ldap2db.pl script and it seems to run - its hard to tell because I don't get any messages at all.  Does anybody know why these users are missing and how to correct it?  Thanks in advance.   -Brian