Hey im having issues with my Innovatek touchscreen, I know how it is man. Lemme mention some things that I haved looked at solving the problem with mine, and see if that can help some.
1. How far is the physical connection from the monitor to the usb input on the motherboard? The USB standard protocol states that it can only accomodate 15 feet, so that might be a reason
2. Check the physical connection on the controller board with a DMM, make sure pin matches up to pin and continuity is attained on both ends of the connectors on the USB end and the micro plug on the controller board inside the screen itself
3. Are the proper USB drivers for your particular motherboard installed?
I wish i could help you more, but those are 3 things ive tried to fix mine and it hasnt helped, ive wished someone on MP3car fourms would of helped me, but hasnt happened.