Xperia X10 Mini/pro :: Turn Off Proximity Sensor?

My problem is that when starting calls I put the phone to my ear and it is muted. The other end hears me, but I dont hear them. This happens most of the time, but not always.I have tested the proximity sensor and the test is OK most of the time and across most of the screen.But since this is creating such frustration, with customers loosing me on the phone, I just want the phone to work as it does on my old HTC Touch Pro:When starting a call the screen automatically goes blank and I cannot accidentally touch the mute button or anything else.Can I do this on my X10 Mini Pro?Alternatively, can I move the mute button to somewhere else on the screen or remove it entirely?