Twitchy Stepper With LiquidCrystal

I’m having trouble having both a stepper motor and a LCD display connected to my Duemilanove. The stepper just twitches back and forth while the LCD works perfectly fine. This only happens when I define the LCD. Once I comment that line out, the motor works perfectly. If anybody can help me out, that’d be great. Thanks.

LCD: http://www.hacktronics.com/LCDs/16-x-2-LCD-White-on-Blue/flypage.tpl.html?keyword=lcd
Motor Shield: http://adafruit.com/products/81

#include <AFMotor.h>
#include <LiquidCrystal.h>

AF_Stepper rotationalMotor(100, 1);               //Define the rotating stepper motor object for relay 1
LiquidCrystal lcd(12, 11, 10, 7, 6, 5, 4);  	//Define the LCD

void setup()
{
    Serial.begin(9600);
    rotationalMotor.setSpeed(10);  //Set rotation motor to 10 rpm   
}

void loop()
{
    rotationalMotor.step(1, FORWARD, DOUBLE);  //Steps the rotation motor  in one direction
}

I think you have a lot of pins clashing there - the motor shield uses D4 to D12 as far as I can see, you can't use pins for two purposes simultaneously.

Is it possible for me to use both the motor shield and the LCD at the same time?

I read some stuff about a backpack. Is a serial backpack the same as a regular LCD but just using less pins? Is it possible to make a backpack myself, or do I have to purchase one? Thanks.

EDIT
Can I use a combination of digital and analog pins for the LCD?