as of last night i started having the same issue.
it started with screen went dark and wouldn't come back. so I rebooted and the screen remained dark and never booted.
I did a soft reboot (grn+menu+red) and then held (home+red) to get into recovery mode (still black screen with back light on. hit (alt+l) to get to the menu and flashed a factory reset. (not recommended without a data plan on phone)
as of now the phone continues to not boot, so when i do power it off, i go though the above sequence though instead of factory reset just do a soft reboot (grn+menu+red) and the phone boots up.
however, now when the phone is left inactive, or the screen times out and goes black, I struggle with button combinations to bring it back. ive de activated the screen time out, and once i watched it literally fade to black.
ive no idea whats causing this its an original phone bought one of the first ones off the line and haven't had a single problem up until this point. running all factory updates, no mods, very few applications, definitely not any in the last several months.