That is because a touch down is not a mouse down. Max6 is not fully touch compliant which is why it does not respond properly. One work around would be to convert all touch messages to mouse messages using something like TouchMousePointer. Which would turn your multitouch monitor into a huge single touch mouse screen.

Thanks, I tried touchmousepointer, it doesn't work very well because the new mouse postition is continuous and doesn't refer to the exact position of the finger. Plus Ubutton still outputs mousedown and mouseup at the same time. But you're right I will search for this kind of app a way to convert touch messages into mouse messages.