I just posted a similar problem here:
Re: Photoshop CS6 issue with shortcuts and my keyboard after upgrade from CS5
with Photoshop CS6 and Yosemite (both clean installs). This is NOT affecting InDesign, Illustrator or Acrobat, only Photoshop. I tried every suggestion in this thread without luck. Guess I'm going to resort to reinstalling as it's impossible to work with shortcuts.