Q: Mac mini: Keyboard and Trackpad irresponsive

Hi

I have a late 2010 Mac mini (in perfect condition) and I love it.  It has worked flawlessly till now until I recently installed Yosemite.  The keyboard and trackpad are irresponsive (freeze) when I wake the computer from sleep.  The monitor would wake up though. 

I have tried to restore the default sleep settings and tried every other setting but to no help.  Eventually I wiped out the hard disk and reinstalled Yosemite and its not helping either.  This problem did not exist before Yosemite installation.  PLEASE PLEASE HELP.  Its become a big issue and I have to shut down the Mac mini several times each day and I keep losing my work.

BIG THANK YOU!