Commented Issue: WP7 Turnstile animation shows blank screen [8293]

I'm using Turnstile animation in my Windows phone application for page transition. If I click the back button too fast, then it shows a blank screen. I removed the turnstile animation and it works fine. Is this an issue with the toolkit? Do you guys have any fix for this issue?
Comments: ** Comment from web user: wieser_software **

The crux of when this goes wrong is when in OnNavigating, _storedNewTransaction != null

If that's the case, it's going to fail.

I tried cancelling the navigation like this at the start of that handler:
if (_storedNewTransition != null)
{
// we haven't finished the last one yet. AARGH.
if (e.IsCancelable) e.Cancel = true;
return;
}

however that casued even more problems, as there's know way to know the navigation has been cancelled, and as a result, I can't re-enable my buttons.