Erratic Mouse Movement

Does anyone here know why a mouse would have erratic stacatto (jumpy) type movements rather than a smooth even movement. You would think that it was snapping to object snap, and yet they are all turned off. With the object snaps on, I am unable to snap to each end of an object to get a linear dimension. The crosshairs jump to either side of what I want to select. The same condition occurs with several different versions on two different machines. Thanks in advance, G. De Angelis

If you're running a mouse with the roller ball inside, it sounds as though the rollers inside the mouse are dirty.......

Dan