Unigrid with Custom Table

I am trying to setup the unigrid to use a custom table and have been running into all sorts of issues. I have followed the Kentico tutorial successfully (docs.kentico.com/display/K82/UniGrid). But when i try to change the parameters to use a custom table as the object type, I get a "[AbstractUserControl.ShowMessage]: Page is not 'CMSPage' or missing messages placeholder" error. I've even tried to use a custom table datasource (see below). I'm not sure what i'm missing. I just want the basic functionality to work. Any thoughts?

<div class="cms-bootstrap">
        <ajaxToolkit:ToolkitScriptManager ID="manScript" runat="server" EnableViewState="false" />
        <asp:Label runat="server" ID="lblInfo" EnableViewState="false" Visible="false" />
        <cms:MessagesPlaceHolder ID="plcMess" runat="server" />
        <cms:CustomTableDataSource ID="ctDS" runat="server" CustomTable="customtable.SampleTable" SelectedQueryStringKeyName="ItemID" />
        <cms:UniGrid ID="ugSteps" runat="server" ShowObjectMenu="false" PageSize="All">
            <GridActions>
                <ug:Action Name="edit" CommandArgument="Name" Caption="$General.Edit$" Icon="Edit.png" />
                <ug:Action Name="delete" CommandArgument="Name" Caption="$General.Delete$"
                    Icon="Delete.png" Confirmation="$CheckoutProcess.ConfirmDefaultProcess$" />                   
                <ug:Action Name="view" Caption="$General.View$" FontIconClass="icon-eye" FontIconStyle="allow" />
            </GridActions>
            <GridColumns>
                <ug:Column Source="##All##" Caption="$CheckoutProcess.Order$" Wrap="false" ExternalSourceName="StepOrder">
                </ug:Column>
                <ug:Column Source="Caption" Caption="$CheckoutProcess.Caption$" Wrap="false">
                </ug:Column>
                <ug:Column Wrap="false" Width="100%" />
            </GridColumns>
        </cms:UniGrid>
        </div>

protected void Page_Load(object sender, EventArgs e)
{
    // Registers the default CSS and JavaScript files onto the page (used to style the UniGrid)
    CSSHelper.RegisterBootstrap(Page);
    ScriptHelper.RegisterBootstrapScripts(Page);

    // Assigns a handler for the OnAction event
    //UserGrid.OnAction += userGrid_OnAction;
    try
    {

        ugSteps.DataSource = ctDS;
        ugSteps.DataBind();
    }
    catch (Exception ex)
    {
        plcMess.ErrorText = ex.ToString();
    }


}