I'm after some advice from those more experienced with LCD's than I !

I'm in the process of taking a project off the EasyPIC5 development board and building the prototype on stripboard. My 20 x 4 LCD has been fitted with a female header which plugs directly onto the pins on the EasyPIC board, so to make life easy I've soldered wires to a set of male header pins so I can easily remove the LCD or stripboard if needed whilst I de-bug any errors in my layout. I've wired the LCD up as per the diagram below



However all I get is a backlit LCD - not even rows of blocks when the device is powered up. I've tripple checked each wire to make sure it's going to the right pins on PORT B and checked the board to make sure there are no shorts / breaks (as far as I can see). My first thought was that the PIC isn't running, so connecting up a sensor caused an indication LED to flash as it should. I've also used an LED to check to see if any voltage is present on RB0 - RB5 and noted that some ports were pulsing the LED much the same way as the leds on the EasyPIC board did, so it would seem that the PIC is running OK. I've used a 10K trim pot, which seems to have no effect, but then if the LCD isn't drawing anything I guess there will be nothing to adjust. - If I place the LCD back in the EasyPIC board with no PIC I get two rows of blocks, but If I remove the PIC from the stripboard this isn't replicated.

Any suggestions