Post your script, this is a scripting error after all

Yeah, posting your code helps, but the error message is telling. DO you mean UnityEngine.Collider? "Collider" and "collider" are different. Collider is the class, collider is the instance attached to the gameObject.

sorry if the code shows up 2x here it is:

pragma strict

 var myProjectile : GameObject;
 var reLoadTime : float = 1f;
 var turnSpeed : float = 5f;
 var fireSpeed : float = .25f;
 var muzzleEffect : GameObject;
 var errorAmount ; float = .001f;
 var myTarget : Transform;
 var muzzlepositon : Transform[];
 var turretBall : Transform;
 
 private var nextFireTime : float;
 private var next$$anonymous$$oveTime : float;
 private var DesiredRotation : Quaternion;
 private var aimError : float; 
 
 function start() {
 
 }
 
 function Update() {
 
     if(myTarget) {
     
         if(Time.deltaTime >= next$$anonymous$$oveTime) {
         
             CalculateAimPositon(myTarget.position);
             turretBall.rotation = Quaternion.Lerp(turretBall.rotation, desiredRotation, Time.deltatime*TurnSpeed);
         
         }
     
         if(Time.time>= nextFireTime) {
         
         FireProjectile();
         
         }
     }
 }
 
 
 function OnTriggerEnter(other : collider) {
 
     if(other.GameObject.tag == "Enemy"){
     
         nextFireTime = Time.time+(reloadTime*.5);
         myTarget = other.GameObject.transform;
     
     }
 
 }
 
 function OnTriggerExit(other : collider) {
 
     if(other.GameObject.tag == myTarget){
     
         myTarget = null;
 
     }
 }

 function CalculateAimPosition(targetpos : Vector3) {
 
     var aimPoint = Vector3(targetpos.x+aimError, targetpos.y+aimError, targetpos.z+aimError);
     desiredRotation = Quaternion.LookRoration(aimPoint);
 }
 
 function CalculateAimError() {
 
     aimError = random.range[-errorAmount, errorAmount];
 
 }
 
 function FireProjectile() {
 
     audio.Play();
     nextFireTime = Time.deltaTime+reloadTime;
     next$$anonymous$$oveTime = Time.deltaTime+firePauseTime;
     CalculateAimError();
 
 
 
     for(the$$anonymous$$uzzlePos in muzzlePosition) {
     
     
     Instantiate(myProjectile, the$$anonymous$$uzzlePos.position, the$$anonymous$$uzzlePos.rotation);
     Instantiate(muzzleEffect, the$$anonymous$$uzzlePos.position, the$$anonymous$$uzzlePos.rotation);
     
     }
 }