Having used the Command+M keyboard shortcut to minimize windows in OS X, I'd like to use the same functionality in Ubuntu 10.10. When I try, though, it only brings up the "communications" section of the indicator applet; like so:

In the Keyboard Shortcuts preferences, I have set as the minimize shortcut Mod4+M, which I got by capturing the Apple Command key and the M key. I find no other shortcut using this key combination in Keyboard Shortcuts, and yet I cannot get the window to minimize when using it.

Does anyone know how to override Ubuntu's default usage of this key combination? Thanks!