Unknown error

So i decided to upgrade my unity a few days ago (from 5.0-5.3) when it got within the program stuff starting getting weird i couldn't import images, I couldn't change settings and the game i made's camera was way off and was being stupid, So i decide to uninstall it and reinstall 5.0, but when i opened it i keep getting this error and have no idea what it means, and on all my gameobjects that have scripts saying there's errors and need fixing, in the console i have this error error CS1061: Type UnityEngine.SpringJoint2D' does not contain a definition for enableCollision' and no extension method enableCollision' of type UnityEngine.SpringJoint2D' could be found (are you missing a using directive or an assembly reference?) the script i have this error for is this using UnityEngine; using System.Collections;

public class MouseManager : MonoBehaviour {

 public bool useSpring = false;

 public LineRenderer dragLine;

 Rigidbody2D grabbedObject = null;
 SpringJoint2D springJoint = null;

 float velocityRatio = 4f;     // If we aren't using a spring

 void Update() {
     if( Input.GetMouseButtonDown(0) ) {
         // We clicked, but on what?
         Vector3 mouseWorldPos3D = Camera.main.ScreenToWorldPoint(Input.mousePosition);
         Vector2 mousePos2D = new Vector2(mouseWorldPos3D.x, mouseWorldPos3D.y);

         Vector2 dir = Vector2.zero;

         RaycastHit2D hit = Physics2D.Raycast(mousePos2D, dir);
         if(hit.collider!=null) {
             // We clicked on SOMETHING that has a collider
             if(hit.collider.GetComponent<Rigidbody2D>() != null) {
                 grabbedObject = hit.collider.GetComponent<Rigidbody2D>();

                 if(useSpring) {
                     springJoint = grabbedObject.gameObject.AddComponent<SpringJoint2D>();
                     // Set the anchor to the spot on the object that we clicked.
                     Vector3 localHitPoint = grabbedObject.transform.InverseTransformPoint(hit.point);
                     springJoint.anchor = localHitPoint;
                     springJoint.connectedAnchor = mouseWorldPos3D;
                     springJoint.distance = 0.25f;
                     springJoint.dampingRatio = 1;
                     springJoint.frequency = 5;

                     // Enable this if you want to collide with objects still (and you probably do)
                     // This will also WAKE UP the spring.
                     springJoint.enableCollision = true;

                     // This will also WAKE UP the spring, even if it's a totally
                     // redundant line because the connectedBody should already be null
                     springJoint.connectedBody = null;
                 }
                 else {
                     // We're using velocity instead
                     grabbedObject.gravityScale=0;
                 }

                 dragLine.enabled = true;
             }
         }
     }

     if( Input.GetMouseButtonUp(0) && grabbedObject!=null ) {
         if(useSpring) {
             Destroy(springJoint);
             springJoint = null;
         }
         else {
             grabbedObject.gravityScale=1;
         }
         grabbedObject = null;
         dragLine.enabled = false;
     }

 }


 void FixedUpdate () {
     if(grabbedObject != null) {
         Vector2 mouseWorldPos2D = Camera.main.ScreenToWorldPoint(Input.mousePosition);
         if(useSpring) {
             springJoint.connectedAnchor = mouseWorldPos2D;
         }
         else {
             grabbedObject.velocity = (mouseWorldPos2D - grabbedObject.position) * velocityRatio;
         }
     }
 }

 void LateUpdate() {
     if(grabbedObject != null) {
         if(useSpring) {
             Vector3 worldAnchor = grabbedObject.transform.TransformPoint(springJoint.anchor);
             dragLine.SetPosition(0, new Vector3(worldAnchor.x, worldAnchor.y, -1));
             dragLine.SetPosition(1, new Vector3(springJoint.connectedAnchor.x, springJoint.connectedAnchor.y, -1));
         }
         else {
             Vector3 mouseWorldPos3D = Camera.main.ScreenToWorldPoint(Input.mousePosition);
             dragLine.SetPosition(0, new Vector3(grabbedObject.position.x, grabbedObject.position.y, -1));
             dragLine.SetPosition(1, new Vector3(mouseWorldPos3D.x, mouseWorldPos3D.y, -1));
         }
     }
 }

}

Please help