Apple is still dealing with a number of video card driver issues introduced in MacOS 10.10.
Photoshop CS4 doesn't use the GPU, so won't run into the GPU driver problems.
For the time being, you can disable GPU drawing in Photoshop's preferences. If you need to use the GPU features in Photoshop, then you may want to consider downgrading to a more stable version of MacOS until Apple can release all the fixes for MacOS 10.10.
Turning off the graphics processor for it doesn't work it actually makes it worse. So if photoshop cs4 doesn't use the GPU either I dont know why when I turn off the GPU in photoshop CC it runs even worse.