Particles issues: not moving and ignoring emitter shape

Hello everybody.
I am having a strange issues with particles.
I created an object, assigned a particle system to it and made a prefab.
The problem is that when i try to instantiate it, the particles don’t move at all, they get created, change shape/colour properly but they stand still; this if i instantiate through code.
If i drag the prefab from the inspector into the scene, everything works fine.
I have this code that take care of creating the particle system:

public class ParticleHelper : MonoBehaviour
	// Singleton
	public static ParticleHelper Instance;

	public ParticleSystem HeartEmitter;
	public ParticleSystem CoinEmitter;
	public ParticleSystem StarBurst;

	void Awake()
		// Register the singleton
		if (Instance != null)
			Debug.LogError("Multiple instances created!");
		Instance = this;

	// Create an explosion at the given location
	public void HeartParticles(Vector3 position)
		instantiate(HeartEmitter, position);

	public void CoinParticles(Vector3 position)
		instantiate(CoinEmitter, position);

	public void StarParticles(Vector3 position)
		instantiate(StarBurst, position);

	// Instantiate a Particle system from the prefab
	private ParticleSystem instantiate(ParticleSystem prefab, Vector3 position)
		ParticleSystem newParticleSystem = Instantiate(prefab, position, Quaternion.identity) as ParticleSystem;
		// Make sure it will be destroyed
		Destroy(newParticleSystem.gameObject, newParticleSystem.startLifetime);
		return newParticleSystem;


The particles then gets instantiated in an OnTriggerEnter2D() method like this:

    void OnTriggerEnter2D(Collider2D other)
        if ( == "kiwi")
			ApplicationManager.myScore += points;
            Destroy(this.gameObject);       //the gameobject associated to this script (the gems) gets destroyed

Now…the particle collider is set to box, if i set it to anything else the particles move fine but they ignore the shape of the emitter and act like it’s a sphere.
Again, if i drag from the inspector directly into the scene, everything is just fine.

This makes me think that there is something wrong with how they get instantiated…
I tried new scenes, new objects, and even everything new from scratch, but still same behaviour.
Does anybody know why it happen?
I have read a lot of online tutorials and apparently there is nothing wrong.
Is it a bug with the particle system?
Any help would be appreciated.

Found what the problem was.
The instantiated object rotation is instanced to 0 instead of 270 like my prefab.
Any idea why the rotation is set to zero after the instance is created?