"value cannot be null. parameter name current" when trying to drag button

I have couple of buttons on a WPF Window. When I try to drag them I get an following error in dialog box:

value cannot be null. parameter name current

I do not know how to handle it.

Here is my code:

<Grid>
   <Grid.ColumnDefinitions>
        <ColumnDefinition Style="{DynamicResource MajourColoumnWidth}"/>
        <ColumnDefinition Style="{DynamicResource MinourColoumnWidth}"/>
    </Grid.ColumnDefinitions>
    <Grid Name="ClinicalDetailsGrid1" >
        <Grid.RowDefinitions>
            <RowDefinition  Style="{DynamicResource RowHeight1}"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
           <ColumnDefinition/>
        </Grid开发者_StackOverflow社区.ColumnDefinitions>
        <Button Content="Save" Name="btnSave" Grid.Row="0" Grid.Column="0" 
                VerticalAlignment="Center" VerticalContentAlignment="Center" 
                HorizontalAlignment="Center" Width="100" Height="20"/>
        <Button Content="Bill Payment" Name="btnSave1" Grid.Row="0" 
                Grid.Column="1" VerticalAlignment="Center" 
                VerticalContentAlignment="Center" HorizontalAlignment="Center" 
                Width="100" Height="20"/>
    </Grid>
</Grid>