If you have the same problem as me when you have down loaded Mountain Lion OSX 10.8 here is how to fix it.
If you see a black lined box around your pointer cursor go to System Preferences and open
Accessibility
Go to Zoom and make sure keyboard shortcuts is ticked; untick Use scroll gesture with modifier keys; tick smooth images; untick zoom follows keyboard focus.
Then go to more options and make sure both sliders for max and min magnification are at zero. Click Done.
That sorted it for me. Hope this helps.
If you see a black lined box around your pointer cursor go to System Preferences and open
Accessibility
Go to Zoom and make sure keyboard shortcuts is ticked; untick Use scroll gesture with modifier keys; tick smooth images; untick zoom follows keyboard focus.
Then go to more options and make sure both sliders for max and min magnification are at zero. Click Done.
That sorted it for me. Hope this helps.