AJAX :: Dropdown List Not Binding With CascadingDropDown Extender?

I am trying to create a cascading dropdown list using two dropdown lists in Visual Studio 2008 Professional connecting to a SQL Server 2008 Standard database on my local machine. I have added the two dropdown lists, as well as a CascadingDropDown extenders from the AJAX Control Toolkit that corresponds with the first dropdown list. The problem I am running into is that despite the fact that I have a CascadingDropDown extender for the first dropdown list so far, and the extender is configured properly, the first dropdown list is showing Unbound in Design view. I also don't see a TargetControlID entry in the properties window for the externder.

I hard coded the TargetControlID to the extender in the Source view and, although I am not receiving any dynamic errors from the TargetControlID entry (meaning, the TargetControlID is a valid parameter, and the dropdown list I entered for that parameter exists on the same page), the dropdown list doesn't populate properly and when in Design view, not only do I not see an entry for the CascadingDropDown extender, but the target dropdown list shows as being "Unbound."

A couple of things I want to point out first:

1) I am using Master pages on this site for the header, footer and navigation. The opening and closing <form> tags, as well as the <ScriptManager> entry are in the Master page, not the content pages. I did this with the assumption that at runtime, each page would have the proper <form> tags and <ScriptManager> entry to function properly.

2) I have been able to add a CascadingDropDown extender to a page in Design view (and it initially displays properly), but by the time I have added all of the properties settings to apply it to its corresponding dropdown list, the entry appears normal in Source view but no longer appears in Design view. When I run the page, the dropdown list does not populate. Obviously, I assume that this is related to the dropdown list showing in Design view as being Unbound, but I don't know how to get the dropdown list to recognize that I have a CascadingDropDown extender that is supposed to apply to it.

Here is what the two elements look like in Source view:

<asp:DropDownList ID="ddlCompany" runat="server">
</asp:DropDownList>
<ajaxToolkit:CascadingDropDown ID="cddCompanies" runat="server" TargetControlID="ddlCompany" Category="Company" PromptText="Select a Company" LoadingText="Please Wait..." ServicePath="~/CompaniesService.asmx" ServiceMethod="GetCompanies">
</ajaxToolkit:CascadingDropDown>

To create these, I have been following Joe Stagner's example in his video on the topic (http://www.asp.net/ajax/videos/use-aspnet-ajax-cascading-drop-down-control-to-access-a-database) virtually word for word. I have set up two TableAdapters/DataSets, one for each dropdown list, and the datasets are able to accurately pull the appropriate data from the database, so I know those are working properly. I believe the problem is that the dropdown list isn't binding with the CascadingDropDown extender properly. It wouldn't bother me that I don't see a TargetControlID entry in the properies window for the CascadingDropDown extender, although I have a feeling that the absense of that property is related to the fact that the dropdown list is not binding to the extender. I searched online for causes to this problem, but I wasn't able to find any solutions.