It is normal for display to go blank due to proximity censor while making calls. In my case however,occasionally the display stays blank even after the call gets over. This also happens every now and then when I lock the phone, only to never unlock. At times, the displays backlit switches while unlocking but not all the time. The phone's processor stays awake in both the cases (calling/locking) and the phone rings & vibrates perfectly on making calls. The only option that I have in such cases is to restart the phone. Is anyone facing similar problems with their phones? I've done a factory reset off late but still the problem persists.