Thanks to Robert McLaws for commenting on this post to correct me - the following information is obsolete - please ignore!
Very weird I know but the key combination you need to switch Aero Glass on / off (given that your system's configured for Aero Glass) is Control-Shift-F9
I'm sure there must be a rational explaination as to why such a combo but it's beyond me!
This shortcut was removed from the builds some time ago. It conflicts with a keystroke combo for Visual Studio 2005.