I'm running into an issue with the Shopping Cart Web Part where I cannot proceed beyond the second Live Site step, Registration check.

I've included the web part in my Shopping Cart template page:

<%@ Register src="~/CMSWebParts/Ecommerce/ShoppingCartWebPart.ascx" tagname="ShoppingCartWebPart" tagprefix="cms" %>

<asp:Content ID="Content1" ContentPlaceHolderID="plcMain" Runat="Server">
    <div class="zoneContent">
        <asp:Label ID="lblError" runat="server" CssClass="ErrorMessage"></asp:Label>
        <div>
<cms:ShoppingCartWebPart ID="scCart" runat="server" DisplayStepImages="True" EnableProductPriceDetail="False" UseUpdatePanel="True" ImageStepSeparator="<img class="ShoppingCartStepSeparator" src="~/App_Themes/BlueRhinoCom/Images/ShoppingCart/Separator.gif" alt="Separator" />" EnableViewState="true" />
        </div>
    </div>
</asp:Content>

The store configuration is using the generated default steps with no changes.

I can add products to the Shopping Cart, and when I cllick the "Check Out" button, it goes to the Registration check step. However, if I try to log in with a registered user, register a new user, or proceed with an anonymous user, the page just reloads the Registration step with no error messages.

I've tried debugging the shopping cart control through /CMSModules/ECommerce/Controls/ShoppingCart.ascx, and when I'm on the Registration check step and click the "Next" button and then step through the code, I'm seeing something strange.

When it gets to the line this.CurrentStepControl.ButtonNextClickAction(); in the btnNext_Click handler, if I add a watch to this.CurrentStepControl, the object type of that control comes back as:
{ASP.cmsmodules_ecommerce_controls_shoppingcart_shoppingcartcontent_ascx}
If I step into the ButtonNextClickAction() method, it loads the code for /CMSModules/ECommerce/Controls/ShoppingCartContent.aspx and runs the IsValid() and ProcessStep() methods for that control, instead of for the ShoppingCartCheckRegistration.ascx.

I've double checked the Checkout process, and the Registration check step is pointing to the ShoppingCartCheckRegistration.ascx page. Am I missing a configuration setting for the ShoppingCartWebPart control, or is this a bug?

We're currently on hotfix 4.1.12. But looking through the hotfix notes for 13 through 21, I didn't see any mention of a fix to ShoppingCartWebPart.ascx or mention of a problem with the control moving through the Registration check step.