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I assume your connected over wifi and using a wireless mighty mouse. The large amount of radio waves being emitted from your computer to your router is interfering with your wireless mouse. Happens to my logitech mouse as well.
 
there is an issue with 2.4GHz frequecncies. Mine were eliminated when I got a dualBand router with 5GHz wireless N. WRT610N.. not the exact solution as it is a pretty expensive router but it is something to note. :eek:
 
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