Q: Why do I keep getting "connection lost" when I begin work on my desktop Apple

I have an IMac desktop computer about 5 years old now.  It has been updated very recently.  As I begin working with my mouse I get a "connection lost" signal and it is becoming more and more frustrating since I basically have a frozen arrow.  I have taken the mouse in the Apple store and they say it isn't a mouse problem.  I've changed batteries in the mouse.  I've tried a new mouse.  Is there something wrong with the hard drive?  Help