Offline Address Book - Outlook 2003 Cached Mode

I have a user who is having Outlook 2003 trouble.  We have an Exchange 2003 Server and he runs Outlook 2003 in cached mode.  His mailbox is fairly large, but recently, he continually has problems with opening Outlook (it continually says it's been closed improperly and needs to do a check of the file...which takes a VERY long time), and he also has problems sending emails.  The sending problem happens when he sends email (not all emails though).  It just hangs and hangs for about 10 minutes before it finally sends.  He also claims it usually sends the message twice, but I haven't watched him to see the process in action.  I thought I would start by removing Outlook and reinstalling it.  Then re-setup outlook in cached mode to create a new OST file.  Well, Outlook doesn't uninstall fully, but that's another topic.  Anyway, after I removed his mail profiles and created a new one, I expected Outlook to start the sync process where it goes through all his folders in his mailbox and build the local OST file.  However, I am seeing a Send/Receive Dialogue box that is taking forever to send and receive from the exchange server.  It says that it's "Copying offline address book details file"  but it's just sits there at 15% progress and doesn't move.  We have many laptop users running with locally cached Exchange mode in Outlook and I have never seen this.  I also don't understand what the offline address book is and I have also heard of a global address book, and I am not sure what that is or how it's used in Exchange/Outlook.  Isn't everyone's "address book" just their Oulook Contacts?  Why is it called offline address book, and why is his outlook hanging up trying to download it?