It happens just the same with my A470 (firmware GM1.00E E18, Jan 8 2008): there is no way to switch off the LCD via software/script, but plugging a jack in the output socket. Only worked once with older build I do not remember and a script that includes an option to switch off the display after n frames/shots (lua script by Fraser McCrossan; accurate intervalometer with power-saving and pre-focus, a really great contribution).