I just installed the RTM version of IE7 and still having an issue with OWA (Outlook Web Access) on Exchange 2003. I have tried two different servers from three different clients and IE generates an exception when I hit the send button after composing an email.

I found a few references to uninstalling the S/MIME control using the "Add/Remove Programs" Control Pannel but attempting that resulted in a rather comical error: "Another version of this prodcut is already installed... use Add/Remove Programs on the Control Panel."

The short term solution is to disable the S/MIME ActiveX control in IE7. Tools -> Internet Options -> Programs -> Select the "Managed add ons" button at the bottom. Then select the "Add-ons that have been used by Internet Explorer" from the drop down list. Select the "Mime Control Version Class" from the list and disable it under the settings.

Seems to solve the issue for me.