Character controller problem

I have a problem with my code that the animations is locked at their finish state and isGrounded is never true after the first time the player moves. It also continues to go in one direction.

 function Update() {
     var controller : CharacterController = GetComponent(CharacterController);
     if (controller.isGrounded) {
         isSliding = false;
         var hit1 : RaycastHit;
         if(Physics.Linecast(transform.position, -Vector3.up , hit1,  2.5) ) {
             var cosAngle = Vector3.Dot(Vector3.up, hit1.normal);
             if(cosAngle <= slideAngle) {
                 isSliding = true;
                 var moveSpeed = (1 - cosAngle)*speed;
                 //The steeper the hill, the faster we slide.
                 moveDirection = new Vector3(hit1.normal.x , -hit1.normal.y , 0);
                 moveDirection = moveDirection.normalized;
                 moveDirection = transform.TransformDirection(moveDirection);
                 moveDirection *= moveSpeed;
             }
             anim.SetBool(FallHash, true);
         }
         if (!isSliding) {
             var j = 0;
             if (Input.GetButton("Jump")) {
                 j = jumpSpeed;
             }
             moveDirection = Vector3(Input.GetAxis("Horizontal"), j, Input.GetAxis("Vertical"));
             if (moveDirection.x != 0 || moveDirection.z != null) {
                 anim.SetFloat(SpeedHash, 1);
             } else {
                 anim.SetFloat(SpeedHash, 0);
             }
             moveDirection = transform.TransformDirection(moveDirection);
             anim.SetBool(SprintHash, Input.GetButton("Sprint"));
             if (Input.GetButton("Sprint")) {
                 moveDirection *= sprintSpeed;
             } else {        
                 moveDirection *= speed;
             }
             anim.SetBool(FallHash, false);
         }
     }
     // Apply gravity
     moveDirection.y -= gravity * Time.deltaTime;
     controller.Move(moveDirection * Time.deltaTime);
 }