advice needed for linear actuator control

re: mike, glad i could be of help.

just had another quick question regarding this thread, hoping someone might be able to shed some light.
After getting the linear actuator working with the H-bridge driver SN754410 I had lying around (http://uk.farnell.com/jsp/search/productdetail.jsp?sku=9592997), I wanted to find a more suitable driver that could produce the 2A required for the linear actuator in question (the one i had tested with could only output 1.2A.. and I want to be able to get the maximum out of these motors).

I ordered the following component : http://uk.farnell.com/jsp/search/productdetail.jsp?SKU=403295 - which appears to be able to output 2A (per channel), however I cannot seem to get it to work, should it behave the same way as the other h bridge adapter?
I have wired it up as follows:

output 1 & 2 => motor pins
supply voltage => 12v external supply
input 1 & 2 => arduino pins 2, 3
enable a => arduino
gnd => gnd
logic supply voltage => arduino + 5v

the code i have (same as the one tested succesfully on the SN754410) is real simple :

  const int motor1Pin = 2;    // H-bridge leg 1 (pin 2, 1A)
  const int motor2Pin = 3;    // H-bridge leg 2 (pin 7, 2A)
  const int enablePin = 4;    // H-bridge enable pin
  const int clutchPin = 8;

void setup() {


    // set all the other pins you're using as outputs:
    pinMode(motor1Pin, OUTPUT); 
    pinMode(motor2Pin, OUTPUT); 
    pinMode(enablePin, OUTPUT);
    pinMode(clutchPin, OUTPUT);


    // set enablePin high so that motor can turn on:
    
    digitalWrite(clutchPin, HIGH); 
    
    Serial.begin(9600);  
  }
  
  
  void loop() {
    // if the switch is high, motor will turn on one direction:
       if (Serial.available()) {

    char ser = Serial.read();

     if(ser == 'a'){
      digitalWrite(enablePin, HIGH); 
      digitalWrite(motor1Pin, LOW);   // set leg 1 of the H-bridge low
      digitalWrite(motor2Pin, HIGH);  // set leg 2 of the H-bridge high
      delay(1200);
      digitalWrite(enablePin, LOW);
     }
     if(ser == 'b'){
       digitalWrite(enablePin, HIGH);
      digitalWrite(motor1Pin, HIGH);  // set leg 1 of the H-bridge high
      digitalWrite(motor2Pin, LOW);   // set leg 2 of the H-bridge low
      delay(1200);
      digitalWrite(enablePin, LOW);
     }
     if (ser == 'c'){
       digitalWrite(clutchPin, LOW);
       delay(100);
       digitalWrite(clutchPin, HIGH);
     }
     if (ser == 'd'){
       digitalWrite(clutchPin, LOW);
     }
  }
  }

but i cannot get any response out of the motor, is there a difference in the two h-bridge adapters that i have missed? should i wire this up differently?

any help would be greatly appreciated