I guess they should work, it crashs on the line where he want to create the box.
Thus the other commands work above - it seems that gPhysicsSDK work.
I guess the cubeMaterial isnt valid - could you replace it with planeMaterial ?
It would be nice when you show us how you initalize your cubeMaterial,
and the other important things.
When this wont work, create your box actor like this: (I´ve changed it to your code)