If the setup uses a high voltage for the backlight and you connect them to the wrong pins you could fry it.
People often suspect the hardware when the code or their connections to the hardware is bad.
If you hook it up correctly and slowly adjust the contrast from min to max you should see black boxes. Back if off so the black boxes just go away and it should be set good enough to see characters.
If you get to this point you know the power connections are right. You still have data connections and code to worry about.