I thought mine was water damamge but i fixed it by downloading
BB desktop software
then do a back up so all you information is saved
go into you apllications delete anythin you downloaded for my it was skysports but can be anythin.
whilst connected to you pc or laptop turn your phone off.
If you lucky the screen will come back on showin you connected to the pc/laptop its liek a white screen witha mobile and computer symbols
close BB desktop software then turn mobile back on thats how i fixed mine.
was completely lucky for me as i wasnt aimin for this just happened to work.
if your unlucky it might be a hardware fault buy a new screen from ebay and replace it your self plenty of videos on how to on youtube and its really easy and allot cheaper.
hope this helps ppl somewhat