On my Mac, running Jaguar I use a Kensington Orbit trackball on my left hand to give my right hand some relief from common scrolling and dragging tasks. However sometimes the Orbit seems to lose its reversed settings, and reverts to the default, which is set up for right hand use. If you look in the preference pane for the Orbit when this happens, you'l l discover it doesn't think the Orbit is plugged in. After much fruitless searching of the support site I accidentally discovered the solution the other day. Just disconnect it and reconnect it again, and it will go back to normal.