asp.net gridview index error - asp.net

Question

I have a gridview which was working fine.
It has some hidden columns, then visible columns.
When I clicked on each row, VB code behind gets values from each column value in the selected row and puts the value in separate textboxes underneath the gridview, eg
txtProjectId.Text = GridView1.SelectedRow.Cells(2).Text.ToString ' project ID
All worked fine.
Find below gridview code (made shorter) as per requested.
<div id="div_GRIDVIEW" class="div_Gridview" clientidmode="Static" runat="server" >
<asp:GridView ID="GridView1" Width="1370px" runat="server" AllowPaging="True" AllowSorting="True" OnSelectedIndexChanged = "OnSelectedIndexChanged" OnRowDataBound = "OnRowDataBound"
cssclass="STD_GridView L4" AutoGenerateColumns ="False" DataKeyNames="Id" DataSourceID="SqlDataSource2" PageSize = "5" GridLines="Horizontal" EnableViewState="False" >
<rowstyle cssclass="GridRowStyle HoverableRow" />
<alternatingrowstyle cssclass="GridAlternateRowStyle HoverableRow" />
<PagerStyle BackColor="#56b7e9" ForeColor="White" HorizontalAlign="Center" width="1370px" Height="20px"/>
<SelectedRowStyle BackColor="#eeeeee" />
<SortedAscendingHeaderStyle BackColor="#56b7e9" />
<SortedDescendingHeaderStyle BackColor="#56b7e9" />
<Columns>
<asp:CommandField ShowSelectButton="true" SelectImageUrl="~/images/xxstd/update16.gif">
<ItemStyle CssClass="hiddencol" /><HeaderStyle CssClass="hiddencol" />
</asp:CommandField>
<asp:BoundField DataField="Id" HeaderText="ProjectMainId"><ItemStyle CssClass="hiddencol" /><HeaderStyle CssClass="hiddencol" /> </asp:BoundField>
<asp:BoundField DataField="PDID" HeaderText="ProjectDetailsID"><ItemStyle CssClass="hiddencol" /><HeaderStyle CssClass="hiddencol" /> </asp:BoundField>
<asp:BoundField DataField="PN" HeaderText="PCFlag" ><ItemStyle CssClass="hiddencol" /><HeaderStyle CssClass="hiddencol" /> </asp:BoundField>
<asp:BoundField DataField="DD" HeaderText="OCFlag" ><ItemStyle CssClass="hiddencol" /><HeaderStyle CssClass="hiddencol" /> </asp:BoundField>
<asp:BoundField DataField="OFF" HeaderText="OFFlag" ><ItemStyle CssClass="hiddencol" /><HeaderStyle CssClass="hiddencol" /> </asp:BoundField>
<asp:BoundField DataField="DCF" HeaderText="DCFlag" ><ItemStyle CssClass="hiddencol" /><HeaderStyle CssClass="hiddencol" /> </asp:BoundField>
<asp:BoundField DataField="OnCF" HeaderText="OnCFlag" ><ItemStyle CssClass="hiddencol" /><HeaderStyle CssClass="hiddencol" /> </asp:BoundField>
<asp:BoundField DataField="RF" HeaderText="ReadyFlag" ><ItemStyle CssClass="hiddencol" /><HeaderStyle CssClass="hiddencol" /> </asp:BoundField>
<asp:BoundField DataField="DF" HeaderText="DeclineFlag" ><ItemStyle CssClass="hiddencol" /><HeaderStyle CssClass="hiddencol" /> </asp:BoundField>
....many more hidden columns here (over 50)...
<asp:TemplateField SortExpression="PDID" >
<HeaderTemplate>
<asp:LinkButton ID="lbItem" runat="server" Text="Project#" CommandName="Sort" CommandArgument="Item" tabindex="1000"></asp:LinkButton><br />
<asp:TextBox runat="server" ID="txtS_PDID" CssClass="HF" OnTextChanged="txtItem_TextChanged"></asp:TextBox>
</HeaderTemplate>
<ItemTemplate>
<table >
<tr >
<td class="STD_normal" style="width:50px;font-weight:bold"><%#Eval("PDID")%></a></td>
</tr>
<tr>
<td class="STD_Normal_Grey" style="width:50px;"><%#Eval("Id")%> </td>
</tr>
</table>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField SortExpression="Item">
<HeaderTemplate>
<asp:LinkButton ID="lbItem" runat="server" Text="Project Name" CommandName="Sort" CommandArgument="Item" tabindex="1000"></asp:LinkButton><br />
<asp:TextBox runat="server" ID="txtS_PDID" CssClass="HF" OnTextChanged="txtItem_TextChanged"></asp:TextBox>
</HeaderTemplate>
<ItemTemplate>
<table >
<tr>
<td class="STD_normal" style="width:150px; font-weight:bold"><%#Eval("PN")%>
</td>
</tr>
<tr>
<td class="STD_Normal_Grey" style="width:150px"><%#Eval("DD", "{0:dd-MMM-yyyy}")%> </td>
</tr>
</table>
</ItemTemplate>
<HeaderStyle HorizontalAlign="Left" />
</asp:TemplateField>
</Columns>
</asp:GridView>
</div>
And here is part of the code when row is selected....the index error occurs on Session("txtcurrentID") = GridView1.SelectedRow.Cells(1).Text.ToString :
Protected Sub OnSelectedIndexChanged(sender As Object, e As EventArgs) 'Handles gridview1.SelectedIndexChanged
Session("txtcurrentID") = GridView1.SelectedRow.Cells(1).Text.ToString
Session("txtcurrentPDID") = gridView1.SelectedRow.Cells(2).Text.ToString
Session("PCF") = GridView1.SelectedRow.Cells(3).Text.ToString
Session("OCF") = GridView1.SelectedRow.Cells(4).Text.ToString
Session("OFF") = GridView1.SelectedRow.Cells(5).Text.ToString
Session("DCF") = GridView1.SelectedRow.Cells(6).Text.ToString
Session("OnCF") = GridView1.SelectedRow.Cells(7).Text.ToString
end sub
So now when I click on each row, I get the following error:
Index was out of range. Must be non-negative and less than the size of the collection.
Everything works fine, the gridview displays correctly and the header filters look fantastic.
However I cannot longer click/select each row...
Any ideas ??