Did you replace the LCD Screen by yourself ? In your case, there are two situation. One is that your new LCD sreen is brokem. The other is that the clips of the flex cable is corroded. You have to take off the LCD screen and then use soft cloth wet with alcohol to clear it. If you don't know how to disassemble your phone, you can go to the web site:
YouTube - Blackberry 8530i Take Apart Video for reference.