Need help with my BB Bold 9900...

It has this weird problem of not showing the screen but lighting up at the back and the keyboard and keypad lighting up, however this can't be a screen problem because when you remove the battery and replace it it turns on and everything functions fine then if you lock it using the screen lock or the pass lock it will just go back to the problem of no screen.
I also noticed that when making a call the screen goes blank.
All features work fine but I have no idea of the problem.

 

Bump, come on someone must have the answer...

 

Bump, help please.