>

>private void _AddPanel(string sKey)
>{
>    UserControl control;
>
>    switch (sKey)
>    {
>        case "ship_items":
>            control = new crlShipItems();
>
>            this.Controls.Add(control);

Try changing this.Controls.Add to:

<pre>
this.Controls.Add((UserControl)control);

You may also need to cast the .Left/Top control (or create another reference to the same object with it already cast to the UserControl type).