Just last night, I tried to use my lcd. I had just bought a new one after I thought my last one had broke (it might still work because of this problem). It is the Sparkfun White on Black 5V (not serial). I used the wiring diagram at http://arduino.cc/en/Tutorial/LiquidCrystal
, the library page, and uploaded the HelloWorld from in the IDE. The backlight would work, but no words would come on even when I twisted the pot. I have used lcds before and they have worked.