(novice) Confused by an error in this implementation of The A* Project:

It's a top-down RTS-style interface in a 2d environment. I'm trying to get it so that when the background (represented by a quad with a mesh collider) gets clicked on, the selected units move to the cursor location, while if a unit gets clicked on, the selected units move to the location of the clicked unit:

From the unit script:

Code (CSharp):

1.     void OnMouseOver() {
2.         if (Input.GetKeyDown(KeyCode.Mouse0)) {
3.             Debug.Log("Click Registered.");
4.             gameState.addActiveUnit(gameObject);
5.             highlight();
6.         }
7.         else if (Input.GetKeyDown(KeyCode.Mouse1)) {
8.             Debug.Log("Right clicked.");
9.             driver.thingRightClicked(gameObject);
10.             Debug.Log("Called Driver");
11.         }
12.     }

From the ground script:

Code (CSharp):

1.     private void OnMouseOver() {
2.         if (Input.GetKeyDown(KeyCode.Mouse0)) {
3.             Debug.Log("Click Registered.");
4.             driver.clearActiveUnits();
5.         }
6.         else if (Input.GetKeyDown(KeyCode.Mouse1)) {
7.             Debug.Log("Right clicked.");
8.             driver.thingRightClicked(gameObject);
9.             Debug.Log("Called Driver");
10.         }
11.     }

From the driver script:

Code (CSharp):

1.     public void thingRightClicked (GameObject thingClicked) {
2.         Vector3 destination;
3.         switch (thingClicked.tag) {
4.             case "unit":
5.                 destination = thingClicked.transform.position;
6.                 break;
7.             case "ground":
8.                 destination = Input.mousePosition;
9.                 break;
10.             default:
11.                 destination = new Vector3(0,0,0);
12.                 break;
13.         }
14.         foreach (GameObject unit in gameState.getActiveUnits()) {
15.             unit.GetComponent<Unit>().move(destination);
16.             Debug.Log("Called unit.move");
17.         }
18.     }

From the movement script in the Unit game-object.

Code (CSharp):

1. void Start() {
2.         seeker = GetComponent<Seeker>();
3.     }
4.  
5.     public void setDestination (Vector3 destination) {
6.         seeker.StartPath(transform.position, destination, OnPathComplete);
7.         Debug.Log("Destination set.");
8.     }
9.  
10.     void OnPathComplete (Path finishedPath) {
11.         Debug.Log("Yay, we got a path back. Did it have an error? " + finishedPath.error);
12.         path = (ABPath) finishedPath;
13.     }

The program only malfunctions when the ground is clicked on: when the seeker.Startpath method gets called with the mouse location as a parameter, it does return a path, but the path has zero points in its vectorPath list. An ArgumentOutOfRangeException occurs soon thereafter.

I'm stumped! Any insight would be appreciated.

 

(Solved: I wasn't converting screen coordinates to world coordinates.)