I would open a support case to get a more definitive answer from PTC. I would suggest this is a driver issue. It may even be a problem with enhancement software that your graphics card OEM has provided. I remember something of a "priority" application I received with mine. These "enhancements" should always be disabled to track down any odd behavior.
I am not sure if there are limitations to dual screens. That would seem odd as it is a fairly common scenario for CAD people.