I had a similar problem. After putting on the security updates last night,
Outlook 2007 Beta would not open correctly, showing this error: "Either there
is no default mail client or the current mail client cannot fulfill the
messaging request. Please run Microsoft Office Outlook and set it as the
default mail client."

I am running IE7 Beta and Microsoft Office 2007 Beta.

In Add or Remove Programs, I uninstalled these patches:
917334 Word, 917953 TCP/IP, restart
918439 ART Image Rendering, 911280 Routing and Remote Access, restart
914389 SMB restart

But none of that fixed it.

I then ran System Restore to a System Checkpoint from 6-12 and that fixed it.

I think it has something to do with the recent updates. But I have never
updated the Junk Email Filter, and it did not appear in Add/Remove Programs,
so I don't think it updated automatically.

"Sam Steinhauser" wrote:

After installing the security updates today, my Outlook no longer worked. It
prompted to run Outlook and make it the default mail client.
--
Sam