Scott:
Can you please post a schematic of how you have the parts inter-connected. Show us in particular how the control signals to each of the chips and the LCD are wired. With this information it will be much easier to consider how the software operates the interface you have created and thus maybe be able to lead to a discussion of what is wrong.

My hunch is that you have something not quite correct in the control sequences and that there is bus contention going in your circuit.

Michael Karas