Why do i get ArgumentOutOfRangeException?

I'm working on a quest system. Everything is working exactly as intended, and all the funtionality is perfect.
The problem is happening when i have multiple quests at the same time in my quest tracker.

If i comlplete the quest in the blue ring, it works perfectly because its the last one in my list.

But if i complete one of the above ones, like the red ring, i'll get this exception:

Could someone help me understand this?

here's the code in which the error is happening:

Code (JavaScript):

1. #pragma strict
2.  
3. var gold : int;
4. var exp : int;
5.  
6. var acceptedQuests : List.<Quest> = new List.<Quest>();
7. var completedQuests : List.<Quest> = new List.<Quest>();
8. //var removeQuests : List.<Quest> = new List.<Quest>();
9.  
10.  
11. function Start ()
12. {
13.  
14. }
15.  
16. function Update ()
17. {
18.  
19. }
20.  
21. function OnGUI ()
22. {
23.     GUI.Label (Rect (Screen.width / 2 - 100, 10, 200, 30), "Exp: " + exp);
24.     GUI.Label (Rect (Screen.width / 2 - 100, 40, 200, 30), "Gold: " + gold);
25.  
26.     GUI.Box (Rect (Screen.width - 210,10,200,250), "Quest Tracker");
27.  
28.     var i : int = 0;
29.     for (q in new List.<Quest>(acceptedQuests))
30.     {
31.         var buttonText : String;
32.      
33.         if (acceptedQuests[i].finished == false) // This is where the error is happening.
34.         {
35.             buttonText = acceptedQuests[i].name + " = " + acceptedQuests[i].objectiveCount + " / " + acceptedQuests[i].objectiveReq;
36.         }
37.         else if (acceptedQuests[i].finished == true)
38.         {
39.             buttonText = "Complete " + acceptedQuests[i].name;
40.         }
41.      
42.         var buttonPosY : int = 40 + (25 * i);
43.         if (acceptedQuests[i].showInTracker)
44.         {
45.             if (GUI.Button (Rect (Screen.width - 205, buttonPosY, 190, 20), buttonText))
46.             {
47.                 if (acceptedQuests[i].finished == false)
48.                 {
49.                     acceptedQuests[i].GainObjective(1);
50.      
51.                     Debug.Log ("Objective increased");
52.      
53.                     if (acceptedQuests[i].objectiveCount >= acceptedQuests[i].objectiveReq)
54.                     {
55.                         acceptedQuests[i].Finish();
56.                     }
57.                 }
58.                 else if (acceptedQuests[i].finished == true)
59.                 {
60.                     exp += acceptedQuests[i].rewardExp;
61.                     gold += acceptedQuests[i].rewardGold;
62.                     // Add other rewards here.
63.          
64.                     acceptedQuests[i].Complete();
65.                     completedQuests.Add(acceptedQuests[i]);
66.                     acceptedQuests.RemoveAt(i);
67.                 }
68.             }
69.         }
70.         i++;
71.     }
72. }

The "acceptedQuests" list is filled by a questGiver script. As i click the quest giver and accept a quest, it moves the first quest in the questGivers list, into the end of the "acceptesQuests" list in the script above.

 

Just a quick guess,
since you are removing item there,
maybe you need to put i--; there after the removeAt() line.. ?

 

Perfect. And the solution makes the explanation to problem obvious. Thank you very much