I solved the problem by manually supplying the distinct values in the DistinctValuesLoading
event of the RadGridView.
private void DatagridArchivesOnDistinctValuesLoading(object sender, GridViewDistinctValuesLoadingEventArgs e)
{
if (e.Column.UniqueName == "processingFailureColumn")
{
e.ItemsSource = new List<bool> {true, false};
}
}