SelectedValue which is invalid because it does not exist in the list of items. Parameter name: value

I have a dropdownlist that populates its items via #include something like this:
<!--#include virtual="/media/com/part-co/all-company-dropdownlist.html"--> <%--asp:DropDownList Visible="true" runat="server" ID="ddlComp" OnSelectedIndexChanged="ddlComp_SelectedIndexChanged" AutoPostBack="True" /--%> The list loads properly with all the items and no errors but when I call the onSelectindexchange event by selecting a different value from the list I get the infamous 'ddlComp' SelectedValue which is invalid because it does not exist in the list of items. Parameter name: value error.
I know this error has been addressed a couple of times but I cant seem to find the right answer yet. This logic was working fin ...