I have a problem with Photoshop. When I apply an adjustment, such as curves, Photoshop applies curves for all the layers below it and just to the layer selected (this is not an adjustment layer). I have deleted the preferences and even reinstalled the whole CS4 Suite.
I'm on a mac and I repaired the disk permissions using Disk Utility and I got this message, "Warning: SUID file "System/Library/CoreServices/RemoteManagement/ARDAgent.app/Contents/MacOS/ARDAgent" has been modified and will not be repaired."
When you add an adjustment layer like CURVES, it will affect all layers below. But when you press on a PC Alt + plus the symbol for new adjustment layer (or press LAYER-NEW ADJUSTMENT LAYER from the menu) you will get a popup menu. Select in this popup menu the option USE PREVIOUS LAYER TO CREATE CLIPPING MASK, the adjustment layer will only work for the layer directly below.