I am running Photoshop CS5 and have just upgraded to Yosemite on my Mac. (I added the Java for OSX2014) Nothing works in my Photoshop program...I can't enlarge objects, I get coloured squares in all my picture frames. I hope someone can help me as I use my Photoshop for EVERYTHING!
That sounds like you may be seeing some of the video driver bugs in MacOS 10.10, try disabling GPU drawing in Photoshop and relaunch the app.
Also make sure you have all the Photoshop CS5 updates installed (should be version 12.0.4).