First things first;
Battery Pull?
Does the clock show when you're starting the phone up?
If you answered yes to the BP and no to the Clock... Replace the LCD bud
I had that happen to my Bold..inexplicable...i literally woke up one morning, picked up the phone to see a white LCD screen..wracked my brain, replaced the LCD...bam! Fixed and sold Got a replacement from the great ppl at Rogers w/out them asking me to return the busted LCD one.