I'm working in photoshop cs4. When i click on my layers (so I can work with them), they highlight green. For the last two days, however, they're only turning a darker gray. Then, when I try to work on them, a warning pops up saying the layer is locked or not visible. To bypass this, I have to double click on the layer to get the Layer Style dialog box to pop up. When I exit out of that, the layer becomes active again (turns green). Anyone have any idea why it's doing this? Did I hit some preference setting and not know it?