Rigid body character spins when it hits objects.

If I walk my rigid body into a cube, it'll spin out of control. Now only does this when it hits stuff with it's side, not the top (As far as I know) and the bottom. I don't think providing code is necessary for this question, but I'll post it anyways.

 #pragma strict
 
 var MovementSpeed : float;
 private var MovementVer : int;
 private var MovementHor : int;
 
 function Update() {
     //setting up the movement variables
     MovementVer = Input.GetAxis("Vertical") * MovementSpeed * Time.deltaTime;
     MovementHor = Input.GetAxis("Horizontal") * MovementSpeed * Time.deltaTime;
 
 
     //Stops the character from sliding around when you aren't moving
     if(Input.GetAxis("Vertical") != 0 || Input.GetAxis("Horizontal") != 0) {
     
         rigidbody.drag = 0;
         }
     else{
         rigidbody.drag = 6;
         }
     
 
     }
 
 function FixedUpdate () {
 
         rigidbody.AddRelativeForce(Vector3(MovementHor, 0, MovementVer));
         
 }