Unhandled Exception Error Script

Hello, I am following FPS tutorials for unity, and when I wrote the script for first person controller, it worked, but out of the blue, with nothing changed I get this error that comes and goes saying

"Unhandled Exception: System.UnauthorizedAccessException: Access to the path "C:\Users\UserName\Desktop\FolderName\ProjectName\Temp\Assembly-CSharp-Editor.dll.mdb" is denied."

I changed the name of the user and folder for privacy, but that's the error I get. The script runs completely fine on visual studio, and the script is dragged on the object I am working with.

The main thing that's strange is sometimes I get this error and sometimes I don't. With nothing changed in the script. This has happened with other unity scripts that have already been built by Unity as well.

This is the script i am using though based off the tutorial.

" using UnityEngine; using System.Collections;

public class FirstPersonController : MonoBehaviour {

 // Use this for initialization
 public float movementSpeed = 5.0f;
 public float mouseSensitivity = 5.0f;
 public float jumpSpeed = 5.0f;
 float verticalRotation = 0;
 public float upDownRange = 60.0f;
 float verticalVelocity = 0;

 void Start()
 {
     Cursor.visible = false;
 }

 // Update is called once per frame
 void Update()
 {
     CharacterController characterController = GetComponent<CharacterController>();
     float rotLeftRight = Input.GetAxis("Mouse X") * mouseSensitivity;
     transform.Rotate(0, rotLeftRight, 0);

     verticalRotation -= Input.GetAxis("Mouse Y") * mouseSensitivity;
     verticalRotation = Mathf.Clamp(verticalRotation, -upDownRange, upDownRange);
     Camera.main.transform.rotation = Quaternion.Euler(verticalRotation, 0, 0);




     //movement
     float forwardSpeed = Input.GetAxis("Vertical") * movementSpeed;
     float sideSpeed = Input.GetAxis("Horizontal") * movementSpeed;

     verticalVelocity += Physics.gravity.y * Time.deltaTime;

     if (characterController.isGrounded && Input.GetButton("Jump"))
     {
         verticalVelocity = jumpSpeed;
     }


     Vector3 speed = new Vector3(sideSpeed, verticalVelocity, forwardSpeed);

     speed = transform.rotation * speed;


     characterController.Move(speed * Time.deltaTime);

 }

}"

Just an FYI I am using this tutorial https://www.youtube.com/watch?v=WZLhtsMlrV0, but like I said this seems to be an issue with any tutorial I have used