Not sure how any of your script is set up, but maybe you can piece some of this together with it.

var randomJumper : float ;
var jumping : boolean = false ;
var rangeMin : float = 1 ;
var rangeMax : float = 5 ;
 
function Update(){
   if(!jumping)
      Jump_N_Stuff() ;
}
 
function Jump_N_Stuff(){
   randomJumper = Random.Range(rangeMin,rangeMax) ;
   jumping = true ;
 //do some jump animation clip thing
   yield WaitForSeconds(randomJumper) ;
   jumping = false ;
}

Lo0NuhtiK - Thanks for your help, tweaked my code to mirror yours (it was quite similar anyway), and it worked a treat! I just need to find out why now, for my own benefit! Here was my code:

 var speed = 0.3;
    var speed2 = 0.5;
    var safeZone = 10;
    var turnSpeed = 3;
    var alive = true;

    function start(){

        animation["ArmatureAction"].wrapMode = WrapMode.Once;
        animation["die2"].wrapMode = WrapMode.Once;
        animation["die2"].layer = 1;
        animation["ArmatureAction"].layer = 0;
        animation.Stop();
    }
    function Update () 
    {

        var atp = GameObject.Find("HammyActor");
        var avoidThis = atp.transform.position;

 if (alive){
    var dist = Vector3.Distance(avoidThis, transform.position);

             if (dist < safeZone)

            Chase();

               else Rest();

            }

        }



    function Chase()

    {

    animation["ArmatureAction"].wrapMode = WrapMode.Loop;

    var target2 = GameObject.Find("HammyActor");

    var target = target2.transform.position;

    animation.CrossFade("ArmatureAction");

    transform.LookAt(target);

    transform.Translate(0,0,speed);

    }

function Rest()

    {

    animation["ArmatureAction"].wrapMode = WrapMode.Once;

        animation.CrossFade("ArmatureAction");

    }

And the relevant part of the new, working one..... Thanks again :)

function Update () 

    {

    var atp = GameObject.Find("HammyActor");

    var avoidThis = atp.transform.position;

    if (alive){



       var dist = Vector3.Distance(avoidThis, transform.position);

         if (dist < safeZone)

        Chase();

           else if (!jumping)

           Rest();

        }

    }



function Chase()

{

animation["ArmatureAction"].wrapMode = WrapMode.Loop;

var target2 = GameObject.Find("HammyActor");

var target = target2.transform.position;

animation.CrossFade("ArmatureAction");

transform.LookAt(target);

transform.Translate(0,0,speed);

}



function Rest()

{

var timerandom = Random.Range(1,9);

animation["ArmatureAction"].wrapMode = WrapMode.Once;

jumping = true;

    animation.CrossFade("ArmatureAction");

    yield WaitForSeconds(timerandom);

    jumping = false;

}