Ran across a known issue with Exchange 2010 and IE9. How do I know it was a known issue? I happened to be on the phone with Microsoft Support at the time for another issue...
The error that this combination causes is that you cannot close the Exchange Management Console in Exchange 2010. When you try to close it you receive the error message "You must close all dialog boxes before you can close Exchange Management Console."
My friendly guy on the Microsoft call told me that there is currently no fix - they are expecting to have a patch out around Q4 2011. The current fix, according to him, was "Don't install it. And uninstall it if you have already." I almost forgot to mute the phone before I started laughing. Gotta love when Microsoft tells you to not keep your computer up to date because it will break it...
So I decided to do some research on my own and (easily) found an article here with the fix.
Basically what you need to do is disable the Internet Explorer Enhanced Security Configuration, then add https://localhost to the trusted sites in IE and your good to go.