Humor me, and try a different USB port (or three) on your computer. They’re not all equal, even on the same computer. The absolute worst are laptops, in my experience. Many don’t even meet USB spec, but somehow the vendors get away with it.
Put a decent powered hub on your shopping list. They’re cheap, and you’ll find all your microcontroller projects (not just FEZ) go much more smoothly with reliable power.
Also, you didn’t connect the sensor in reverse by mistake (even for a moment), right? You’d know if you did and had an “aha” moment and rearranged the pins. +3.3v on the ground pin could be bad for that transistor.
You didn’t mention what kinds of values you’re getting.