probably a messed up flex cable that on this phone is part of the keypad membrane.  The flex goes thru the left hinge and is easily pinched.  It does not take but a nick in the flex cable and lots of strange things may happen,ie, white screen, no screen, phone won't boot, some keys won't work.  I fix phones and could probably fix this phone with no problem.
                 Robert
                
 August 2007