When you make phone calls, do you put your ear directly on top of the earpiece, or "hover" over the phone as to not touch it?
I ask because the phone has a sensor near the earpiece that when it can't see light (it's covered) it disables the screen so you can't push buttons. Yet when you pull away from your ear to look at it, it auto-enables.
If you're pushing the hangup button, either you're not covering this sensor to disable to screen, or something is wrong with the sensor itself.
Well, in fact I always try not to touch the screen with my ear and maybe that's the reason for my problem. I didn't know of the existence of such a sensor, but anyway I don't think all models have it. My phone is a Sony Ericsson X10 mini pro.
Anyway, check~ put the phone to your ear during a call. Hold it there, then pull away so you can see it quickly. You should see it turn on from black. Try covering it completely with your hand, etc. If you're hovering over the earpiece, then that's your main issue.
Yeah it happened to me a few times while on hold for an eternity at some online shop, usually right as they took my call before I learned what was causing it. ><