The HTC Desire HD is a decent smartphone but it does not come without problems, for those of you that envy those that own this handset should know that users have been experiencing Proximity Sensor Problems.
If you visit XDA-Developers Forum you will see that owners of the HTC HD Desire are reporting problems with the display screen when making and receiving calls, apparently when making calls the screen seems to deactivate permanently and then makes the phone unresponsive. Many users have then got to pull the battery out and reboot to activate again, which is not good at all.
Receipt of calls conversely keeps the screen on and active, even when pressed against your ear according to Android Police.
The problems seems to be something to do with the light-sensor, this could be down to a bug in the software in which case can be fixed with a software update (OTA), the device should not be shipping with such issues.
According to the sources above you can insert a headset into the jack point and in doing this it wakes the phone up from the previous locked position.
Please do let us know if you are having any problems with your HTC HD Desire, we want to hear from you ASAP so other readers get an insight.