Q The cursor on a colleague’s iMac, using a network account, is likely to suddenly and randomly fly to another point on the screen. This has persisted across changes in Mac, keyboard, and mouse. Is there a misconfiguration in her network account?

A The most common cause of this infuriating behaviour of the mouse pointer is using an optical mouse on an unsuitable surface. This fools the sensors inside the mouse into thinking that it has been moved quite violently.

Try a uniform, medium to dark, and non-reflective surface, such as the plastic workdesk surfaces that are available cheaply from office suppliers. Rarely it can be mimicked by third-party enhancement software, and on Magic Trackpads by inadvertent contact by other digits and parts of the hand. However before considering anything else, put the mouse on a plain dull surface.

Updated from the original, which was first published in MacUser volume 27 issue 13, 2011.