I thought my browser was broken, and it turned out to be me. Until last week, I used a left-handed mouse and Firefox at work. I use a right-handed mouse and Safari at home. When I started to experience some pain in my left middle finger, I switched my work mouse to the other side. Suddenly, alt-click wasn't opening a new tab in my browser. What went wrong? Kernel panic? Preferences reset? Not really: my muscle memory was just trying to use a Mac splat-click with the left hand instead of a Firefox control-click. We are more deeply programmed than we realize.
In retrospect, this is a pretty cool brain hack. You can wire yourself to subconsciously adapt to two different operating systems just by which mouse you use. (If you're ambidexterous anyway.) It doesn't scale, though: I'd need a third arm to use Windows.