Can't bind IsChecked on RadioButton with custom ControlTemplate

Question

I have been using a custom RadioButton control with a ToggleButton as the control template. Here's what the xaml looks like:

    <RadioButton.Template>
        <ControlTemplate>
            <ToggleButton x:Name="tb" IsChecked="{Binding IsChecked, Mode=TwoWay, 
                                RelativeSource={RelativeSource TemplatedParent}}" 
                                      Content="{TemplateBinding RadioButton.Content}"
                          PreviewMouseDown="tb_PreviewMouseDown">
            </ToggleButton>
        </ControlTemplate>
    </RadioButton.Template>

It's been working well, except when I try to either programatically set a button's IsChecked property, or make a binding with it. Then the button that should be checked is visually unresponsive - it doesn't appear to be pressed, and the Aero mouse over effect does not appear. The Clicked event handler still works, and the IsChecked property of both the RadioButton and the ControlTemplate's toggle button are true when I examine their values. Amy I doing something wrong with the binding? Any ideas?

Here's an example of how I use it in the application:

<local:RadioToggleButton Content="1Hr" GroupName="Interval" x:Name="oneHrBtn" 
IsChecked="{BindingPath=oneHrBtnIsChecked, Mode=TwoWay}" Margin="2 5 3 5" 
IsEnabled="{Binding Path=oneHrBtnIsEnabled, Mode=TwoWay}"/>

Answer 1

So the issue with my custom RadioToggleButton control was being caused by something very weird indeed. I will describe my solution below, not because I expect anyone else to run into this particular problem, but just as an example of a solution that seems unconnected to the problem.

There was a binding on IsEnabled property of the GroupBox containing the button group. This binding seemed to work fine, enabling and disabling all the internal controls when appropriate. But as soon as I removed this binding, the problem I described above disappeared. This is not ideal, but I decided that I had spent too much time on this issue, so I bound the IsEnabled properties of the individual controls to the same property that the GroupBox had been bound to, and now at least I have the behavior I wanted.