if you want faster shutter, up the ISO to its max. but then you'll get noise. also, use full wide angle to get the largest aperture. if you tried using 1/1500 shutter at night, you'd get nothing but black.

but that might not even work as the sd400 has pretty limited control to begin with.

that's due to a slower refresh rate. if your camera didn't "lag" the LCD display, then there wouldn't be enough light for each frame and all you'd see is black on the LCD.