4.6.0 to 4.6.1 makes player lag, bug?

Hi, so I was working on a prototype for my game and was using the 4.6.0 version. When I updated to the current version of 4.6.1, my character seemed to randomly start lagging and I have no idea why. I used the same code for both of them and made no modifications. To make my player move I used rigidbody2D.AddForce. I've tried uninstalling and re-installing unity multiple times and keep having the same problem. A weird though, the background doesn't lag, just the player does. I made a little demonstration and uploaded it to YouTube:

4.6.1 Video

4.6.0 Video

Could it be a problem with one of my settings? I know that on the 4.6.1 Release Notes it mentions something about Physics2D and such. I thought this was the reason but it doesn't mention anything about the AddForce function.

Here's the code I used. The movement code is in the update function and I don't see any problems with it:

 using UnityEngine;
 using System.Collections;
 
 public class Player : MonoBehaviour {
 
     public float speed = 4f;
     public bool surfaceTouch = false;
     public bool SurfaceFall = false;
     public ParticleSystem Splash;
     public ParticleSystem Sand;
     public ParticleSystem AirBubbles;
 
     private Animator anim;
 
     // Use this for initialization
     void Start () {
         rigidbody2D.gravityScale = 0;
         Sand.emissionRate = 0;
         Splash.emissionRate = 0;
         AirBubbles.emissionRate = 0;
         anim = gameObject.GetComponent<Animator> ();
         StartCoroutine (bubbleAir ());
     }
 
 
 
 
     
     // Update is called once per frame
     void Update () {
     
 
         if (Time.timeScale == 1) {
             //Face Mouse
             Vector3 mousePos = Input.mousePosition;
             mousePos.z = 0f;
             
             Vector3 objectPos = Camera.main.WorldToScreenPoint (transform.position);
             mousePos.x = mousePos.x - objectPos.x;
             mousePos.y = mousePos.y - objectPos.y;
             
             var speedTurn = 500f;
             
             float angle = Mathf.Atan2 (mousePos.y, mousePos.x) * Mathf.Rad2Deg;
             Quaternion qTo = Quaternion.Euler (new Vector3 (0, 0, angle));
             transform.rotation = Quaternion.RotateTowards(transform.rotation, qTo, speedTurn * Time.deltaTime);
 
 
             //Movement
             var pos = Input.mousePosition;
             pos = Camera.main.ScreenToWorldPoint (pos);
             var dir = pos - transform.position;
             rigidbody2D.AddForce (dir * speed);
         }
 
 
         //Animation
         anim.SetInteger ("state", 0);
         var absVel = Mathf.Abs (rigidbody2D.velocity.magnitude);
         if (absVel < 1f) {
             anim.speed = 0.1f;
         } else     if (absVel > 1f && absVel < 3f) {
             anim.speed = 0.3f;
         } else     if (absVel > 3f && absVel < 5f) {
             anim.speed = 0.7f;
         } else     if (absVel > 5f) {
             anim.speed = 1f;
         }
     }
 
 
 
 
     void OnTriggerEnter2D(Collider2D col){
         if (col.gameObject.tag == "Surface") {
             //Splash
             if(surfaceTouch == false){
                 surfaceTouch = true;
                 Splash.gravityModifier = -1;
                 Splash.emissionRate = 100;
                 StartCoroutine(splash());
             }
         }
         //Sand
         if (col.gameObject.tag == "Floor") {
             var absVelY = Mathf.Abs (rigidbody2D.velocity.magnitude);
             if (absVelY > 1) {
                 Sand.emissionRate = 30f;
                 StartCoroutine (stopSand ());
             } else if (absVelY < 1) {
                 Sand.emissionRate = 15f;
                 StartCoroutine (stopSand ());
             }
         } 
     }
 
 
 
 
 
     void OnCollisionEnter2D(Collision2D col)   {
         if (col.gameObject.tag == "Surface") {
             var absVelY = Mathf.Abs (rigidbody2D.velocity.y);
             if(absVelY < 0.5){
                 rigidbody2D.gravityScale = 0.6f;
                 SurfaceFall = true;
                 StartCoroutine( SurfaceDown() );
             } else if (absVelY < 1 && absVelY > 0.5){
                 rigidbody2D.gravityScale = 1f;
                 SurfaceFall = true;
                 StartCoroutine( SurfaceDown() );
             } else if (absVelY > 1){
                 rigidbody2D.gravityScale = 1.5f;
                 SurfaceFall = true;
                 StartCoroutine( SurfaceDown() );
             }
         }
     }
 
 
 
 
 
 
     //spash
     IEnumerator splash(){
         yield return new WaitForSeconds (0.3f);
         Splash.gravityModifier = 1f;
         yield return new WaitForSeconds (0.4f);
         Splash.emissionRate = 0;
         surfaceTouch = false;
     }
     //Sand
     IEnumerator stopSand (){
             yield return new WaitForSeconds (0.5f);
             Sand.emissionRate = 0;
     }
     //Surface
     IEnumerator SurfaceDown(){
         if (SurfaceFall == true) {
             yield return new WaitForSeconds(0.2f);
             rigidbody2D.gravityScale = 0;
             SurfaceFall = false;
         }
     }
     //Air bubbles
     IEnumerator bubbleAir(){
         var bubbles = 5;
         while(bubbles > 0){
             yield return new WaitForSeconds (10);
             AirBubbles.emissionRate = 7f;
             yield return new WaitForSeconds(2);
             AirBubbles.emissionRate = 0f;
         }
     }
 
 }
 

If you have any ideas what this could be, I'm all ears! Thanks!