Nikon D300 Digital Camera "focus error r11" Questions

the focus ring. An error code of r11 appears in the LCD. Is something wrong with the camera? Can I solve the problem or does it need repair? This might be obvious, but is the AF / M switch still on AF

page 36 it speaks about the buffer. The r with a number is how many shots the buffer at that moment can handle. It is not an error message. For auto focus issue is the lens in AF as well as the camera

...error indication. Depending on the mode, the camera either will or will not allow you to take the shot when the image is out of focus. Make sure the lens is set to A for auto, and try to focus on ...