on collision loading a new level

Hello All I have a short game with about 5 levels.

As the FPS Cam navigates along a path they collide with an invisible plane that has a javascript on it to load level on collision.

Sometimes it works and sometimes not,

(rather it works in Unity, but not all the tim in iOs. All levels are listed in the game settings, so that's not it)

I am running the 5 beta and the colliders must be convex.

Any Ideas? Thanks in Advance

Here's the javascript:

 #pragma strict
 
 var levelToLoad : String = "nextLevel";
 
 function OnTriggerEnter(other : Collider) {
   Application.LoadLevel(levelToLoad);
 }