[TheMostToys]

I have the stock screen protector on and the proximity sensor works for me. To test, make a call and place your hand against the top left of the face of the phone (above the screen between "HTC" and the speaker) and my screen turns off. BTW, the proximity sensor is only active while actively in a call.
On my TP1 I got in the habit of pressing the power button to turn off the screen when in a call, and if I needed to turn the screen back on, just press it again.