gridview deleting error EnableEventValidation="true" but Invalid postback or callback argument error
<p>in my project i have a master page , usercontrol and webforms using master page.
my usercontrol consists of textboxes buttons and gridview 
on one of my pages when i try to delete the column confirmation message box shows up then i click ok and then that error sows up and 
i need to say that when i make EnableEventValidation="true" at the top of my page the error doesnt show up but doesnt go to deleting event too</p>

<blockquote>
  <p>Microsoft JScript runtime error: Sys.WebForms.PageRequestManagerServerErrorException: Invalid postback or callback argument.  Event validation is enabled using  in configuration or &lt;%@ Page EnableEventValidation="true" %> in a page.  For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them.  If the data is valid and expected, use the ClientScriptManager.RegisterForEventValidation method in order to register the postback or callback data for validation.</p>
</blockquote>

<p>the strange part is there is no such a thing at the other page that i use the user control.
here are my codes</p>

<p>thats my gridview</p>

<pre><code>&lt;asp:UpdatePanel ID="UpdatePanel1" runat="server"&gt;
    &lt;ContentTemplate&gt;
        &lt;asp:GridView ID="grdKatilimci" runat="server" AutoGenerateColumns="False" 
            DataKeyNames="SICIL"  
            CellPadding="1" CellSpacing="1" BorderWidth="0"
            EnableModelValidation="True" onrowdatabound="grdKatilimci_RowDataBound" 
            onrowcommand="grdKatilimci_RowCommand"&gt;
            &lt;Columns&gt;
                &lt;asp:BoundField DataField="SICIL" HeaderText="Sicil No" ItemStyle-Width="55px" /&gt;                                                                       
                &lt;asp:BoundField DataField="AD_SOYAD" HeaderText="Ad- Soyad" ItemStyle-Width="200px"&gt;                                    
                &lt;/asp:BoundField&gt;
                &lt;asp:BoundField DataField="BOLUM" HeaderText="Bölüm" ItemStyle-Width="136px"&gt;
                &lt;/asp:BoundField&gt;
                &lt;asp:BoundField DataField="DEPARTMAN" HeaderText="Departman- Mağaza" ItemStyle-Width="136px"&gt; 
                &lt;/asp:BoundField&gt;
                &lt;asp:BoundField DataField="GOREV" HeaderText="Pozisyon" ItemStyle-Width="136px"&gt;
                &lt;/asp:BoundField&gt;                                    
            &lt;asp:TemplateField&gt;
                &lt;ItemTemplate&gt;
                &lt;asp:ImageButton CommandName="Sil" ImageUrl="~/Foto/del.jpg" runat="server" CommandArgument='&lt;%# Eval("SICIL") %&gt;' OnClientClick="return confirm('Bu kullanıcıyı silmek istediğinize emin misiniz?');" /&gt;
//the above is confirmation msg
               &lt;/ItemTemplate&gt;
                &lt;/asp:TemplateField&gt;
            &lt;/Columns&gt;
        &lt;/asp:GridView&gt;                                               
    &lt;/ContentTemplate&gt;
    &lt;Triggers&gt;
    &lt;asp:AsyncPostBackTrigger ControlID="lnkKatilimciEkle" EventName="click" /&gt;
    &lt;/Triggers&gt;
&lt;/asp:UpdatePanel&gt;
</code></pre>

<p>that is row command event of my gridview</p>

<pre><code>protected void grdKatilimci_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        if(e.CommandName=="Sil")
        {

            string sicil = e.CommandArgument.ToString();
            OdbcConnection cnn = new OdbcConnection(mth.sConnection);
            OdbcCommand cmd = new OdbcCommand();
            cmd.Connection = cnn;
            cmd.CommandText = "DELETE FROM EDU_KATILIMCI WHERE SICIL_NO=" + sicil + " AND ID_EGITIM='" + lblId.Text + "'";
            cmd.CommandType = CommandType.Text;
            cnn.Open();
            cmd.ExecuteNonQuery();
            cnn.Close();
            mth.FillGridView("SELECT (ADI ||' '|| IKINCI_AD ||' '|| SOYAD) AS AD_SOYAD, EP.SICIL, EP.GOREV, EP.DEPARTMAN, EP.BOLUM FROM EDU_PERSONEL EP INNER JOIN EDU_KATILIMCI EK ON EK.SICIL_NO =EP.SICIL WHERE EK.ID_EGITIM='" + lblId.Text+"' ORDER BY ADI", grdKatilimci, "");            
        }
    }
</code></pre>
