I didn't have this issue on the first MD I built because I just hardwired the LCDs, but this time, I used the pin headers to make things easier to build...well it turns out that the vishay 16x2 LCDs I was using have the pins flipped in a different orientation-the only way to use header pins would be to pass them through the front of the LCD and then there is not proper room for mounting them:
http://www.vishay.com/docs/37300/37300.pdf
So in other words-at least with the vishay's, you must hard wire them...I found out too late, and burned out both of my LCDs
(I know they are burned out because I have a working MD here and swapped out the LCD and it works correctly...