As for the PK3, its power capability is very low as Pommie said. How low? It is really not in the specifications last time I looked, but I have read it is about 20 mA.
For your LCD, are you sure it is not the program? Is it parallel or serial? If parallel, are you using fixed waits after toggling E or monitoring the busy flag? I have gotten odd characters when timing is off. There is also a prescribed power-on-reset protocol that should be followed for either serial or parallel LCD's.
John