Spotlight captures middle mouse click
OS X 10.9.3, Macbook air late 2010.
I need to use some X11 software on a remote computer which requires middle and right mouse clicks.
I have tried producing the required mouse clicks in two ways: using an ancient Kensington blue tooth 3-button mouse OR using MagicPrefs to set multi-finger trackpad clicks to middle or right clicks. Either way works BUT either way the middle click is captured by OS X and instead of being sent to the remote program, it toggles the Spotlight search window instead.
How can I disable this unwanted OS X feature?
MacBook Air, OS X Mavericks (10.9.3)