Working on a friend's laptop today I found that his mouse is very hard to control. Even when my hand was nowhere near it the pointer was skittering around. I know how to change the sensitivity of the mouse for clicking, etc; but how can we stop the hyperactivity? My friend has returned to using the touchpad as that is more under his control.
axelbrora's suggestion may do the trick. It is indeed an optical mouse on a shiny and light mouse mat. I'll go round tomorrow with a spare mat that I have that isn't shiny or light and see if that cures it. Thanks everyone.