GridView hides when clicking a button?

Hi, 

I have a GridView that has 10 fields, 6 are normal, 7th is a CheckBox, 8th, 9th, 10th are buttons. 

7th - CheckBox is a tempate Field. The rest are normal. 

<asp:GridView ID="GridView2" runat="server" AllowPaging="True"
                AutoGenerateColumns="False" DataKeyNames="UserName,ID"
                onrowcommand="GridView2_RowCommand" Width="1053px"
                style="text-align: center"
                onrowdatabound="GridView2_RowDataBound"><Columns><asp:BoundField DataField="ID" HeaderText="ID" /><asp:BoundField DataField="RequestedDate" HeaderText="RequestedDate" /><asp:BoundField DataField="DeanDirectorName" HeaderText="DeanDirector" /><asp:BoundField DataField="UserName" HeaderText="UserName" /><asp:BoundField DataField="PhoneExt" HeaderText="PhoneExt" /><asp:BoundField DataField="RoomNo" HeaderText="RoomNo" /><asp:TemplateField HeaderText="Approve"><ItemTemplate><asp:CheckBox ID="CheckBox1" runat="server" Checked='<%# Bind("Approve") %>'
                                 /></ItemTemplate><EditItemTemplate><asp:CheckBox ID="CheckBox2" runat="server" Checked='<%# Bind("Approve") %>' /></EditItemTemplate></asp:TemplateField><asp:ButtonField CommandName="View" HeaderText="View" Text="View" /><asp:ButtonField CommandName="Approve" HeaderText="Approve" Text="Approve" /><asp:TemplateField HeaderText="Decline" ShowHeader="False"><ItemTemplate><asp:Button ID="btnDecline" runat="server" CausesValidation="false"  OnClick = "btnDecline_Click"
                                CommandName="Decline" Text="Decline" /></ItemTemplate></asp:TemplateField></Columns></asp:GridView>

Now when I open the Form with GridView, it opens up well. But when I click on the Decline Button,. the whole GridView gets lost. 

It does give me an error. It says: "Specified cast is not valid"

It gives at this location: 

<asp:CheckBox ID="CheckBox1" runat="server" Checked='<%# Bind("Approve") %>' 

Any ideas? 

some error occurs here, and so the GridView doesnt load and exits.