BB Torch :: Unable To Work If Connected To The Mains?

I have had a 9860 Torch for 15 months with Orange now, with no problems to mention. The phone however started to play up, the battery seem to run dry very quickly and I had to put it on charge daily without having used the phone much, ie no bluetooth, not surfing the net etc. Then the phone started to go off when I took it off charge. The screen would go black and only the butons at the bottom would be alight. Nothing would happen if I pressed any of the buttons, and I am not able to restart the phone. I then have to put it on charge again, take the battery out and re-insert it, and it will start up again as long as it is connected to the mains. The battery indicator shows the battery is fully charged, I did however buy a new battery and downloaded the latest update just before Christmas, which seemed to solve the problem for a few days, however the phone has now reverted to the same problem. The phone works perfectly well when connected to the mains, but the screen goes black as soon as it is disconnected, and will only start up again if connected back up to the mains and battery taken out and re-inserted.