Multiple storyboards in a wpf application - wpf

Question

I have three storyboards in a wpf application.
begin is single animation
progress is a repeating animation
end is a single animation too
All storyboards animating the same image, the "progress" storyboard is repeating (while a query in an another thread is running), the "begin" storyboard preceeds it, the "end" animation follows it.
I supposed that this is a simple problem: when the application starts, start the "begin" animation, then in an oncompleted event handler, starts the progress animation, etc.
But it doesnt work: the progress animation is starts, but it appears improperly (strange flashing).
I made a "button1" to analyse this, and i noticed then the same method in the button's onclick eventhandler is works (after the begin storyboard is ended, i pushed it, and the progress storyboard is started and appeared perfectly).
(The FillBehavior of the begin animation is "Stop": the button doesnt worked without this setting, but the eventhandler is remains wrong after setting it)
private void Window_Loaded(object sender, RoutedEventArgs e)
{
begin = (Storyboard)FindResource("startanimation");
progress = (Storyboard)FindResource("progressanimation");
end = (Storyboard)FindResource("stopanimation");
begin.Completed += new EventHandler(begin_Completed);
begin.Begin();
}
void begin_Completed(object sender, EventArgs e)
{
progress.Begin(); //not works
}
private void button1_Click(object sender, RoutedEventArgs e)
{
progress.Begin(); //works
}
Any idea?

Answer 1

Try this:
void begin_Completed(object sender, EventArgs e)
{
this.Dispatcher.Invoke(
System.Windows.Threading.DispatcherPriority.Normal,
new Action(
delegate()
{
progress.Begin();
}
));
}

Answer 2

Eventually I am forced to make a secondary timer, and start the progress animation in the tick event.. Very ugly, but works.
Any other tips are still welcome.