Hmm, I followed the circuit here
http://ecomodder.com/wiki/images/7/7..._Schematic.GIF that shows a PNP (2N3906) although I used a 2N4403 (somewhat equivalent, also PNP) as it was what I had on hand. Is there a version that uses an NPN instead? I'm using a blue w/ white letter 16x2 standard HD44780 LCD if that makes any difference.