I have reported this as a bug already, but am curious if anyone has ran into it and has a workaround.  Whenever the theme property is programatically changed, any toggle buttons that are drawn within the ribbon are rendered as though they are unchecked, even if they really should be checked.  If you hover your mouse over the button and then back out it is rendered properly.  See below for code.

<Window x:Class="WPF_Ribbon_ToolTip.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:igRibbon="http://infragistics.com/Ribbon"
    Title="Window1" Height="300" Width="400">
    <Grid>
        <igRibbon:XamRibbon x:Name="XamRibbon1" >
            <igRibbon:RibbonTabItem>
                <igRibbon:RibbonGroup>
                    <igRibbon:MenuTool Caption="Test" ButtonType="SegmentedState" IsChecked="True">
                        <igRibbon:ButtonTool Caption="SubButton" />
                    </igRibbon:MenuTool>
                    <igRibbon:ToggleButtonTool x:Name="tb1" Caption="Test1" IsChecked="True" />
                </igRibbon:RibbonGroup>
            </igRibbon:RibbonTabItem>
        </igRibbon:XamRibbon>
    </Grid>
</Window>

namespace WPF_Ribbon_ToolTip
{
    /// <summary>
    /// Interaction logic for Window1.xaml
    /// </summary>
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();

            XamRibbon1.Theme = "Office2k7Black";
        }
    }
}