I was complaining a while back that I couldn't get my Logitech M-BA47 rodent's fourth button to do anything but be an alternate second button. I went out and bought an Apple Mighty Mouse, which I'm pretty happy with.
While unplugging my Logitech mouse to take it in to work (it was better than the wheel-less thing I had there), I found the culprit. You know those little USB to PS/2 adapter plugs some mice have? Turns out this was one of those. When I plugged the now-USB mouse directly into the USB bus, all of the sudden the fourth button started generating a unique event.
Today's tip: unplug the hardware defunctionalizer. (B)