Nothing in preview for smart sharpen and unsharp mask

IMac with uptodate OS X. CS4 Extended. When I try to use the unsharp mask or smart sharpen tools there is nothing in the preview area, just white. The video card is an ATI 2600 PRO with the Open GL enabled in Photoshop preferences. I've tried disabling the Open GL in PS but this disn't work. I've tried using the KB and can't find a reason/solution to this situation. Please help.

Thanks

Wayne Beyea

Is the layer highlighted that you want to sharpen or have you accidentally highlighted an adjustment layer?