Problem getting value from DropDownList/ListBox/CheckBoxList

I have one DDL and one ListBox/CheckBoxList/DDL (Doesnt matter which one id used) and a filled SQL DataSource via codebehind.
I dont have any problemas with the firs DDL, but at the time that i want to get the value from the second one, the selected item change to a especific one, with index(1). It only happens with one function (SelectUser()).
<asp:ListBox ID="libTest" runat="server" DataTextField="FullName" DataValueField="ID" AutoPostBack="false"> </asp:ListBox>
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libTest.DataSource = usrBll.SelectUsers() libTest.DataBind() -----------------------------------------
Public Function SelectUsuarios() As List(Of Usuario) Dim _managersql As New CORE_ConnectionManager
Dim sqlCom As SqlCommand = _managersql.GetCommand(CommandType.StoredProcedure, "spSelectUsers")
Try
Dim _UserDAL As Ne ...