Hi

when I minimize the ribbon, the place under the ribbon is shown as a black rectangle.

any hints what i'm doing wrong ?

<igRibbon:XamRibbonWindow
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:bemvvm="http://schemas.be-it.net/winfx/2011/xaml/mvvm"
    xmlns:s="clr-namespace:System;assembly=mscorlib"
    xmlns:igRibbon="http://infragistics.com/Ribbon"   
    xmlns:igEditors="http://infragistics.com/Editors"
    xmlns:igWindows="http://infragistics.com/Windows"    
    x:Class=MailWindow"
    x:Name="Window"
    Title="Window"
    Width="640" Height="480" Icon="Web_GlobalAppClass.ico">
  <igRibbon:RibbonWindowContentHost>

        <igRibbon:RibbonWindowContentHost.Ribbon>
              <igRibbon:XamRibbon Height="144" x:Name="xamRibbon1" DockPanel.Dock="Top" Theme="Office2010Blue" QuickAccessToolbarLocation="AboveRibbon">
           
            <igRibbon:XamRibbon.ApplicationMenu>   
                <igRibbon:ApplicationMenu Caption="Datei">
                    <igRibbon:ButtonTool Caption="Open"  />
                    <igRibbon:ButtonTool Caption="Close" />
                </igRibbon:ApplicationMenu>
            </igRibbon:XamRibbon.ApplicationMenu>
            <igRibbon:XamRibbon.QuickAccessToolbar>
                <igRibbon:QuickAccessToolbar >
                    <igRibbon:QatPlaceholderTool>
                       
                        </igRibbon:QatPlaceholderTool>
                </igRibbon:QuickAccessToolbar>
            </igRibbon:XamRibbon.QuickAccessToolbar>
            <igRibbon:RibbonTabItem Header="Entitäten" />
        </igRibbon:XamRibbon>
        </igRibbon:RibbonWindowContentHost.Ribbon>
    
    </igRibbon:RibbonWindowContentHost>
 
</igRibbon:XamRibbonWindow>