User unable to open attached email messages - but can open other attachments (Excel, Word, pdf, etc)

I have a Windows XP Pro user on our company network (on Windows 2003 LAN with MS Exchange Server 2003) using MS Outlook 2003 SP3.  He is a relatively new employee - started beginning of this year (2007).  Anytime someone sends him an email message and attaches another email message within it, (instead of it coming to him as a thread), he cannot open the attachment.  He sees it - the little envelope icon.  He double-clicks on it. Nothing happens.  I even try right-clicking on it and clicking "Open". Nothing. There's no error, there's no message going across the top of the email saying that Outlook blocked the attachment.  I turned off his Google toolbar and Google desktop.  I deleted his email profile and re-created.  I moved the email message to another folder - from the server to a pst file. Didn't help.  I was about to just uninstall and reinstall but I think it's overkill.  Just hoping I could find something in here.  But I didn't see anything so I'm asking a new question.