Phone screen doesn't light up?

For the past few days I have been noticing whenever I get a call on my Samsung Behold, I hear the ringtone, but the screen doesn't light up (It happens randomly). Just wondering is there anything wrong with my phone or am I missing something? BTW my Behold is only few months old, I got it from WireFly (with a new T-Mobile account) through a discount deal available at http://www.dealrocker.com/promotions/wirefly/deals/. I appreciate any assistance you experts can provide.

Thanks..

exact same thing happens to me! started about 2 days ago. whenever i get a call, the screen goes black and none of the buttons work, so i cant pick up any phone calls.

i am able to make calls, but the screen still goes dark.  Therefore, when i make a call, i cant touch the keypad to enter my Voicemail or turn on speaker phone.

if there is something wrong with that sensor, is it fixable?

Thats how its suppose to be

problem for me is when the screen goes dark, the hard buttons don't work either.

there doesn't seem to be anything blocking it, but I'll try to take it apart and look under the screen.

the LCD connector loose ,open the phone there is connector under the board.