Error problem

I have a character that fires projectiles. I’ve animated it so that when i go into the animator and click the bool isattacking he starts to shoot. As soon as he shoots I get the error:

Setting the parent of a transform which resides in a prefab disabled to prevent data corruption.
UnityEngine.Transform:set_parent(Transform)

The line that this is connected to is my fire function

here it is:

private void Fire()
{
GameObject newProjectile = Instantiate(projectile) as GameObject;
newProjectile.transform.parent = projectileParent.transform;
newProjectile.transform.position = gun.transform.position;
}

The line unity has problems with is the second one about parent. Now in Monodevelop there seems to be no problems. Does anyone know how to resolve this error?

Please use code tags when posting code.

The code you posted should work fine. The problem must be elsewhere.