2d and character controler

I have a problem with 2d toolkit and character controller, it does not start the if statement that supposed to play walk animation (it it stuck in the idle). can someone point out what am I missing?

 [...]
 
 function Update ()
 {
 var anim : tk2dAnimatedSprite;
 anim = GetComponent(tk2dAnimatedSprite);
 
 var controller : CharacterController = GetComponent ( CharacterController );    // set controller to character controller
     
     if( controller.isGrounded )                            //if character on ground
     {    
         velocity = Vector3 ( Input.GetAxis("Horizontal"), 0, 0 );
     
         if ( velocity.x == 0 )         //idle 
         {
         if (anim.isPlaying() && anim.CurrentClip.name != "idle")
         {
         anim.Play("idle");
         }
         }
 
         if ( velocity.x < 0 )                            //walk left
         {
         velocity *= walkSpeed;                            //move left based on the walkspeed
             
         if (anim.isPlaying() && anim.CurrentClip.name != "walk")
         {
         anim.Play("walk");
         print ("walk_left");
         }
         }    
 
                 
         if( velocity.x > 0 )                            //walk right
         {    
         velocity *=walkSpeed;                            //move right based on the walkspeed
             
         if (anim.isPlaying() && anim.CurrentClip.name != "walk")
         {
         anim.Play("walk");
         print ("walk_right");
         }
         }
 [...]