Outlook 07, Exchange 03 Error 80040115

Hi Guy,
I have a users running off of a Vista Ultimate Ed laptop getting an 80040115 error message when he attempts to send mail, (or use send/ receive) in Outlook 07. This is stopping him from sending any emails.

Additional Note:
Exchange Server: Windows SBS 2003, SP1 using Exchange 2003 Enterprise Ed.

No other users are experiancing this problem. Although he is the only one using Vista and Outlook 07 together. They are some users who use XP and Outlook 07 together.

Any suggestions to the cause of and resolution to the problem is?

Thanks.
chuck.