Was their sun light falling directly on the screen? The touchscreen is not really a touch screen - it has IR sensors along the sides that detect where your finger is over the screen - and can become mute with sunlight on it.
lmeans said:I got into my MDX after work one day and I put it on the blue screen so I could turn down the fan. I touched the fan and nothing happened, so I'm touching all over the screen and nothing. I used the mouse and it worked. So I tried the touch screen again because this really bothered me and it worked.