This seems to have occurred after a soda spill on my D5100. Everything else seems to be working normally.
The 'Up' button on my multi selector is not always working: in menus I cannot move up to an item I have moved past; when I am viewing an image "full screen" the 'Up' button does not display the image info.
However, if I view an image and zoom in, the up arrow moves me up the zoomed image, as expected. Similarly if I am in 'Live View' the up arrow will move the focus selection.
I have reset the Shooting and Playback menus.
Any suggestions would be gratefully received!