For the part you need, the wiring is pretty simple. Before we get to that, lets do the sanity check:
#1 Verify you have +5v and +3.3v on the board. I don't know the pinouts for the voltage regulators, but the three pads for each device are connected back to the AT power plug. Where the 7805 would be installed, you should have 12v, 5v, and gnd (0v) on the three pads - I don't know the order, but if you put the black lead of a multimeter into the backside of one of the black wires on the AT connector, that's what you should see. Where the other voltage regulator goes, you should see 5v, 3.3v, and gnd.
edit - I forgot about the GND input power connector - you can also use that for your black lead when making measurements.
#2 Did you program the PIC with the "SmartString_Hub.hex" file.
If yes and yes and still no joy, try swapping the two 485 chips close to the PIC with two of the others on the board.
If still no joy, it's time to start traciing wires and checking vias - vias are the holes that run through the board. They are supposed to be plated-through to connect one side of the board to the other. On very rare occasion, you have to solder a short piece of wire to make the connection...
RM