How to keep PowerPoint from mirroring my monitors when switching apps? When I'm in presentation mode in PowerPoint 2008, and I deliberately or accidentally switch to another app, PowerPoint forces my dual monitors into mirrored mode.

Apart from shrinking my desktop and repositioning many dozens of windows, this also forces fullscreen virtual machines onto my main monitor, such that I can't get at the menu bar without unzooming them (and consequently messing up their desktops).

Does anyone know how I can prevent PowerPoint from doing this?  Does PowerPoint 2011 do the same thing?  (And does it introduce yet another incompatible UI?)
If you switch PowerPoint to display mode first, then switch to a mac app (using command-tab), then turn off mirroring, the setting should then stick. Otherwise, as you found out, Microsoft is sure nobody but powerpoint needs display mode.

In case some reader doesn't know how to turn off mirroring: If you go into "System Preferences/Display Preferences" Arrangement tab (only present when connected to a second display), uncheck the box that says "Mirror Displays".

Also, on the bottom of the Display Preferences pane, you can check "Show displays in menu bar" to access this setting more easily without going into preferences.