Flash Build - swallows coroutines

I've finished building my C# simulation to Flash, including browser communication, json serialization/deserialization, and everything works great in FireFox. However, when I run the same exact simulation in IE or Chrome some of the coroutines are being swallowed up.

So this code was started with a coroutine (StartCoroutine(OnSimMessage(args));

     private IEnumerator OnSimMessage(NotificationArgs args) {
                 // This statement makes it to the log
                 Debug.Log("Before Yield Sim Message");
                 
                 yield return new WaitForSeconds(1);    

                   // this statement never runs
                 Debug.Log("After Yield Sim Message"); 
                 // Do some other logic
     }

Again this ONLY happens in IE and Chrome. It seems like even a smaller subset of coroutines actually run in Chrome than in IE.

The difficulty here is that some coroutines ARE working, but others are not, and I have no ideal why this would be browser dependent. I thought that was the beauty of Flash, was build once, run anywhere.

I realize this is probably obscure, but anyone think of a reason why this would be happening? It's killing me right now.