Exchange Contacts

Hello. I recently upgraded someone's e-mail to Outlook 2003. He was originally on a POP3 server. I moved him over to our Exchange 2003 server. Since then, he has duplicate Contacts. He modify's one - and the other one does not get modified. I tried every setting I could find to only do a search on the Contacts folder. Not Actuv Directory, Exchange - or anywhere else. And he still has duplicate contacts when he does a search. But if you go to his Contacts - there are no dups. Ugh...help...