MarketplaceReviewTask Crash

Windows Phone
1

I am getting a crash when my game runs the following code.

  if (CurrentItem == ratepos && CurrentTask != TastType.Rate)

{
                    TaskTimer = DateTime.Now.Second * 60 + DateTime.Now.Minute;
                    MarketplaceReviewTask r = new MarketplaceReviewTask();
r.Show(); //a few seconds after running this it crashes.
                    CurrentTask = TastType.Rate;
                }

now the same code runs fine on an xna game, but crashes on mono with this error
`An unhandled exception of type ‘System.Reflection.TargetInvocationException’ occurred in System.Windows.ni.dll

Additional information: Exception has been thrown by the target of an invocation.`

Any suggestions?

2

Never mind this was caused Due to an this

 Deployment.Current.Dispatcher.BeginInvoke(() =>

{
                        InAppPurchase(CurrentItem);
                    });

It was been run at a similar time and cause the crash.