Sporadic Failure to Catch BrowserInvokeEvent

We've run into a problem where the BrowserInvokeEvent either isn't firing or isn't recognized. Our app is based in javascript and this is the first thing that we're running:

air.NativeApplication.nativeApplication.addEventListener( air.BrowserInvokeEvent.BROWSER_INVOKE, handleBrowserInvoke );

Most of the time it works great, however, we have run into a few machines that won't trigger the event listener. We have been unable to find a common factor in the machine's and have even run into the problem where identical machines will produce different results. One works and the other does not. Are we missing something basic in the way that we are listening or handling the BrowserInvokeEvent? Or is there another event we need to listen for before initializing the BrowserInvokeEvent?

Thanks,
Ben