Have you spilled something on the unit? I heard of this happening once and it was because the DJ had spilled a drink and the sugars had dried around the edge of the button causing it to "activate" when he tapped anywhere on the surface of the controller. Even bass vibrations were causing it to start and stop itself.
If you haven't spilled anything, I suggest you contact technical support for your region (links are located to the right ---->) and have the unit serviced.