When my attached view model has an error the tab gets the red border around it. I tried to disable through the following style but no luck:
<Style x:Key="DocumentWindowStyle" TargetType="docking:DocumentWindow" BasedOn="{StaticResource DockingWindowStyle}">
<Setter Property="FileName" Value="{Binding Path=Text, Mode=TwoWay}" />
<Setter Property="Validation.ErrorTemplate" Value="{StaticResource EmptyValidationTemplate}" />
</Style>