Curious to find this post. I just assembled today an RGB LCD kit (positive) and I'm also having a problem. I've built many hardware interfaces; started back in the 1960's. (ya, OK, I'm old!) The assembly instructions for this kit were excellent.
As I assemble a project, I use an eye loupe to inspect each solder connection. My symptoms are:
on power up and adjusting the contrast pot, I get one (1) row of boxes on the display. Contrast pot is almost all the way CCW. "Hello World" sketch seems to hang at the call to lcd.begin. I'm using a Arduino compatible "Funduino"
as a Duemilanove. Any advice would be most appreciated.