SelectedIndexChanged Event Not Firing

Using VS2005 VB IDE. WebUserControl has 10 dropdown boxes for selecting discreet data options. Box1 is Last Name and Box 2 is First Name and Middle Initial. Select Last Name in Box 1 and Box 2 is populated with all the First Name and Middle Initials tied to the selected Last Name. Simple way to quickly select one individual from a group of >5000. Box 1 is named cboMembers and Box 2 is named cboFirstNames.
Double-clicking cboMembers in design stage places cursor on cboMembers_SelectedIndexChanged subroutine in VB code-behind. HTML code-behind header contains AutoEventWireup="true", <div section shows <asp:DropDownList ID="cboMembers" runat="server" AutoPostBack="True" OnSelectedIndexChanged="cboMembers_SelectedIndexChanged" </asp:DropDownList>
Is this a known problem? I'm dead in the water. The event is not entered (it doesn't hit the debug point at the top of the code).
Surely someone at Microsoft has a fix this by now?
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