Unpredictable Mice

I have a Logitech Mouseman Dual Optical mouse that is driving me insane. At random times the pointer suddenly jumps across the screen, usually on the vertical plane. While this is not too big of a problem doing some tasks, at other times it is unacceptable (for example while playing an online FPS and I get fragged because suddenly I am looking at the sky or ground while my opponent blows me to smithereens).

Any suggestions as to what might be the cause of this?

A couple of things:

  1. Make sure the lenses are clean
  2. Make sure the surface is clean and is of a consistant color

Just to reiterate what Mr. Blue Sky said, optical mice still need some maintenance. You can get the occasional hair stuck in lense surface - and while you can use it on your knee, it’s best to stick a sheet of paper as your mouse pad. My flatmate’s mouse was acting up and we traced the problem to a patterned mousepad.