If you have both circuits sharing the same power supply, then the likely problem is that when the motor has a coil that is engaged, it is basically creating a short and drawing all the power from the rest of the circuit. If memory serves correctly, the 7805 is only capable of 1A max current. My suggestion is to separate the motor form the rest of the circuit by giving creating a dedicated power supply for it. Just be sure to connect the ground of the two circuits.
Also, try to avoid using the same transformer to supply power to both regulators. Using two separate transformers will help keep noise from the stepper motor from rippling into the GLCD circuit.