IPhone :: 4 Black Screen But Phone Works

I have used the iPhone 4 (Factory Unlocked) for more than a year now with only minor issues. Like on a usual day I was playing a word game "Rumble" then quit the game, connected my earphones for music & pressed the "Home" button on the phone to unlock it and the screen was Black. This was a sudden shocker!! . I just put the phone to rest for a while & after about an hour crossed my fingers and tried the Home button again but the Black screen continued. So the backlight of the iPhone works I can say that bcoz I see the phone luminates but the "Slide to Unlock" is cannot be seen. Since I have been using the phone for a while I know the exact position of "Slide to Unlock" so if I slide my finger it unlocks too with the default "unlocking (click) noise" but again the icons of the apps cannot be seen, all I see is a fadely luminated grid. I receive SMS's and Calls although I cant read them nor can I see whos calling. Since the screen is blank I cant operate the phone but the phone seems to be working. I hence tried the reboot, restart, shutdown & start again, restore backup, update iOS everything a desperate user would do but nothing has worked till now. There is not much discussion on this issue anywhere hence No resolution. I am gonna visit an Apple service center today and keep my fingers crossed. I have taken utmost care of the phone. Till date it is scratchless, spotless.

Info:
Apple iPhone 4, iOS 4