Outlook 2007 disconnected from Exchange 2003 on laptop, account works fine from PC

Environment:
Windows Server 2003 SBS, current service packs and updates
Exchange 2003
Windows XP SP2 laptop, connects to server via CAT5 and/or wireless connection

One user cannot connect to the Exchange server from their laptop computer, either via the wired or wireless network connection.   Outlook is configured with the Exchange account, and also with an IMAP connection (for use outside of our company location).  IMAP was able to send/receive mail, Exchange showed an error when trying to send mail.

IOutlook shows "disconnected" from Exchange.   When I clicked File/Connect to Exchange from within Outlook, it was unable to connect.  Now, that choice (connect to Exchange) is not available, but shows "work offline" instead.  After that, IMAP could not send mail either.   All other users are able to use their Exchange and IMAP accounts without any problems.  This issue started a few weeks ago.

Attempted to set up the Exchange account again, shut down Outlook, used control panel "Mail" applet to re-enter Exchange server and user name, no change except IMAP stopped working.  From within Outlook, tried to repair both the Exchange and IMAP accounts, no change, both still not able to send mail.

Running a repair on the Office installation did not change anything with Exchange, but IMAP started sending mail again.  (It had been able to receve mail.)

Tested Exchange & IMAP accounts by setting up same user on a PC in our office.  Exchange connected instantly, and remained connected.  IMAP worked as well.  (We assume that if the user account works perfectly on another computer, then the issue must be with the laptop or local Outlook installation.)

We are looking for the Office 2007 install media, with our next step being a complete removal and reinstallation of Office 2007.   Any suggestions would be greatly appreciated.