Scrollviewer and ItemsControl VerticalScrolling into nirvana - silverlight

Question

Hi i've got a complex ItemsControl wich is used to display news (variable height!) with a slide/fade in effect. (like google currents) my problem now is that the scrollviewer will calculate the available scrollingsize left based on whatever.. that will end up in a very ugly way of scrolling if the user scrolls fast! sometimes the scrollview scrolls into the nirvana. i thought this might be the cause of virtualization but i'm not able to deactivate it. as you can see i ve already replaced the ItemsPanel.
<ScrollViewer
ManipulationMode="Control">
<ItemsControl
Name="TickerItemList"
ItemsSource="{Binding TickerItems, Source={StaticResource TickerViewModel}}"
HorizontalAlignment="Stretch"
HorizontalContentAlignment="Right">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Vertical" />
<!--<VirtualizingStackPanel CleanUpVirtualizedItemEvent="CleanUpVirtualizedItem" VirtualizingStackPanel.VirtualizationMode="Recycling" />-->
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.Template>
<ControlTemplate>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="1*" />
</Grid.RowDefinitions>
<Image Grid.Row="0"
Source="{Binding TitleImage, Source={StaticResource TickerViewModel}}"
Name="TitleImage"
Height="240"
Stretch="UniformToFill"
Loaded="TitleImageLoaded"
CacheMode="BitmapCache"/>
<Grid Grid.Row="1">
<Border Height="15" Margin="0,-15,0,0" VerticalAlignment="Top" >
<Border.Background>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#00000000" Offset="0"/>
<GradientStop Color="#44000000" Offset="1"/>
</LinearGradientBrush>
</Border.Background>
</Border>
<ItemsPresenter />
</Grid>
</Grid>
</ControlTemplate>
</ItemsControl.Template>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid RenderTransformOrigin="0.5,0.5" Tap="ItemTapped" Background="{StaticResource TickerPageBackgroundBrush}">
<!-- RenderTransform definition for animating each item -->
<Grid.RenderTransform>
<TransformGroup>
<ScaleTransform />
<TranslateTransform />
<RotateTransform />
</TransformGroup>
</Grid.RenderTransform>
<!-- Selector for ticker type -->
<local:NinePatch Margin="10,10,10,0" Image="{StaticResource TickerPaperImage}" CacheMode="BitmapCache">
<local:TickerListItemLayoutSelector Content="{Binding}">
too many lines... ;)
</local:TickerListItemLayoutSelector>
</local:NinePatch>
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</ScrollViewer>