So I've been using these nifty optical mice since they came up with the ones that don't require that specialized mirrored mouse pad. Sometimes I wonder if the bloody things are possessed by some evil spirt or something. This seems to be related to lots of incremental small movements, oh like the kind when using something like GIMP or Blender. Anyway you'll be happily tooling along, and move the mouse just a bit to select that vertex, or move that line just a smidge and *ZOOM* there goes the mouse pointer skittering across the screen.

 Quite distracting  if I do say so myself..