Trouble with moving LivingEntities

In one of my plugins I have to tell a Zombie to which point it has to go. The problem is, that the code is just not working and i have no idea why. No errors, nothing.

Code:

Monster monster = Bukkit.getWorld("world").spawn(new Location(Bukkit.getWorld("world"),200, 12, -180), Zombie.class);
Location l = (new Location(Bukkit.getWorld("world"),200, 12, -170));
Block location = l.getBlock();
EntityCreature ec = ((CraftCreature)monster).getHandle();
PathEntity pf = ((CraftWorld)location.getWorld()).getHandle().a(ec, location.getX(), location.getY(), location.getZ(), 16.0f, true, false, false, true);
ec.setPathEntity(pf);

bump

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

Moved to the appropriate section

 

Maybe you can take a look at my navigator class.
Link: here

 

Ok, the mob movement is now working!

Code:

EntityCreature ec = ((CraftCreature) monster).getHandle();
Block to = lv.getLocation().getBlock(); //lv is a LivingEntity and the place where the mob has to go to
PathEntity pf = ((CraftWorld) to.getWorld()).getHandle().a(ec, to.getX(), to.getY(), to.getZ(), 16.0f, true, false, false, true);
if(creep.getMonster() instanceof PigZombie || creep.getMonster() instanceof CaveSpider || creep.getMonster() instanceof Blaze || creep.getMonster() instanceof Enderman) {
        ec.setPathEntity(pf);
}
else {
        Navigation nav = ec.getNavigation();
        nav.a(pf, 0.15f); //The float is the speed of the mob, i dont know the default speed
}

But I got a different problem. s.setTarget() is only working for the mobs in the "if" part. the mobs in the "else" wont attack any LivingEntities