Can't select a layer mask

Photoshop CS5 (latest update) will not allow me to select a layer mask. For example, I have a pixel bearing layer with a layer mask and want to use refine mask. I click on the mask and nothing happens. The layer (not the mask) remains active. Blue is the color that shows a layer is active on my computer, and after I have clicked unsuccessfully on the layer mask the blue color changes to grey. When I attempt to choose any layer now, instead of blue I get grey. I have reset Photoshop preferences which did not solve the problem, so I even uninstalled Photoshop, reinstalled and updated it, and still have the same problem. Any help would be appreciated. Thanks!!