PSP screen......half of it is grey!!!!!

Half of my slim white psp screen is grey. I was just playing a game and it suddenly appeared. Everything else is find ... i can move through the xmb etc...just the grey thing is in the way! Ive turned off the psp a million times rebooted it, tried updating the firmware and nothing seems to work. is it something to do with the LCD inside the psp or software ... i dont think its software but i havent dropped the psp or anything so i dont know??? please help..any help would be useful
thanks

u dropped it maybe???
can u post a pic it would help alot

Prehaps use a pixel fixel. I know the Vista Emulator Portal has one. Google "How to fix stuck pixels" I know Gigafide on youtube has a video about it. It's good.