Some suggestions...

1. Have you remembered the pull-up Resistor on RA4? On any other pin you can dispose with it, but if you use RA4 then it's gotta be there.

2. You sure you haven't got anything miss-wired? RA0 goes to DB4... easy to mistake and connect it to DB0... RS-bit and E-bit are easily cross-connected to the wrong pins...

3. Is your contrast set so dark that everything is blacked-out?

Melanie