One of my friends has a D40X that's been locking up and displaying a warning on the rear LCD. I don't have the exact wording, but it displays a stop sign and asks the user to turn the camera off, then turn it back on. The lens is a first generation 18-200 Nikon VR. One other possible variable is that one of his camera batteries in a non-OEM Duracell brand. This was the battery he was using when it was locking up yesterday. Anyone have any idea as to what might be going on?