I'm sorry to hear about your problem...because I'm having exactly the same
issue! I've got a Dell desktop (about a year old), with Vista, Outlook 2007
(newly loaded), and McAfee. The problem started suddenly about 3 weeks ago,
which makes me wonder if it might have been caused by a Vista update my
machine loaded automatically. I think it's a Vista problem (rather than
Office), because when it first started I was still using Outlook 2003.
Upgrading to Outlook 2007 did not change anything.
Let me ask you a few questions. If you drag and drop an email message from
your inbox to your desktop, are you able to open it by double-clicking? I'm
not able to. If you single-click (left button) on the item in the preview
pane, do you get an error message saying there's a problem with the
previewer? I get that error message.
I have no problem opening any other kinds of attachments.