Re: Possible intallation errors
Photoshop CS4 leverages the graphics display card's GPU, instead of the computer's main processor to speed its screen redraw. For Photoshop to access the GPU, your display card must contain a GPU that supports OpenGL and has enough RAM to support Photoshop functions.
Try this: Go into Photoshop's preferences (Edit > Preferences > Performance ) and uncheck "Enable Open GL Drawing". If that solves the problem you may want to update your display driver to one compatible with CS4.