This is really annoying me on an IXUS 75 aswell. Even with face detect turned off, the white box appears sometimes and the menu dissapears. Also, the circular rocker control has some sort of touch sensitivity so whenever you touch it, the display mode changes back to 'on' and one of the little icons in the top right corner changes to green, forcing a screen redraw and the menu dissapears again. Ofcourse yo have to touch the rocker to navigate the menu so this is really frustrating.