I can't figure out what I did........In the Layers Palette, on each layer, just to the left of the thumbnail, is a little icon that shows whether I'm working on the image or the mask - it's a little paint brush or gray square with a dot in it. Now only the "eye" icon is showing. Can you please tell me how to get that other icon back?
In order to determine whether you are working on the layer or the layer mask Photoshop (pre-CS2) a paintbrush icon or a layer mask icon will appear respectively.
In order to see the icons you'll need to create a Layer Mask first. Since the sample you sent me has no Layer Mask you won't see the icons associated with them. Also, it's important to note that starting with PS CS2, the two icons have been eliminated in favor of a "framed highlight". Slightly less visible, however it does reduce visual clutter.