I'm trying to set up an external table in the admin console to provide a dynamic dropdown on a template.  After registering the external table I was able to click on View and preview the data just fine.  When I change a dynamic field on a template to reference a field in the table, I receive error 9409.

Here's the error stack: 

Error Code: 9409
Error Message: Failed to initialize the external table. [9409]

------------ Technical Details ------------

LFSO:
    Call Stack: (Exception)
        ILFObjectImpl::Update
    Additional Details:
        HRESULT: 0xc00424c1 (LFSession::ProcessResponse, LFSession.cpp:3880)
         (LFSO/9.2.1.568)
LFAdmin.dll (9.2.1.635):
    Call Stack: (Current)
        CDynamicFieldPropPage::OnQuerySiblings
        CTemplate1PropPage::OnApply
    Call History:
        CDynamicFieldPropPage::OnClcEditmessage
         CBoundParentDlg::OnOK
        CTemplate1PropPage::OnApply
         CDynamicFieldPropPage::OnQuerySiblings
         CTemplate1PropPage::TemplateOK
         CTemplate1PropPage::ReadFields
         CTemplate1PropPage::LoadAceData
         CDynamicFieldPropPage::OnQuerySiblings

Table contains four varchar fields (from varchar(10) to varchar(100)) and 200 rows.  Any help would be appreciated.