Outlook 2007 – One user not able to send/receive emails

I have one user who shares a computer with 5 others. This one user is not able to send or recieve email. The other 5 users send and receive just fine. The computer is running XP Pro w/SP2 along with Office 2007. If I go to the users inbox view OWA I can send and receive just fine. What could be wrong with this one users inbox?