Why is my first radiator not being tested?

I got the following Html:

<div class="horizontalRadio">
    <label for="SearchBag.DisplayTypeChips" id="DisplayTypeChipsLabel">
        <%=ViewData.Model.T9nProvider.TranslateById("CommonWeb.Chips")%>
    </label>
    <%=Html.RadioButton("displayType", DisplayTypes.Chip,
        Model.DisplayType.Equals(DisplayTypes.Chip.ToString(), StringComparison.InvariantCultureIgnoreCase),
        new { @id = "SearchBag.DisplayTypeChips" })%>
</div>
<div class="horizontalRadio">
    <label for="SearchBag.DisplayTypeGrid" id="DisplayTypeGridLabel">
        <%=ViewData.Model.T9nProvider.TranslateById("CommonWeb.Grid")%>
    </label>
    <%=Html.RadioButton("displayType", DisplayTypes.Grid,
       Model.DisplayType.Equals(DisplayTypes.Grid.ToString(), StringComparison.InvariantCultureIgnoreCase),
        new { @id = "SearchBag.DisplayTypeGrid" })%>
</div>

      

        
        
        
      

    

Whenever there Model.DisplayType

is a "grid" everything is fine; the second button is checked.
When the value is "chip", nothing is checked. In the debugger I can see that Model.DisplayType.Equals(DisplayTypes.Chip.ToString())

is true. When I change the name of the buttons to something else, this works too.
Sometimes I don't want to change my name because the name makes sense. This is the name I use throughout the application ...

Any ideas WHY is this name evil?