Microsoft JScript runtime error: ASP.NET Ajax client-side framework failed to load

Microsoft JScript runtime error: ASP.NET Ajax client-side framework failed
to load

i hav a gridview in my page and the gridview has a column showing url's of
another page. when i click on the url the page is opened..however when i
click back button i m not able to get back to my page that has the
grid..it gives me the Error "Microsoft JScript runtime error: ASP.NET Ajax
client-side framework failed to load"
Here is the Code of the Grid Page :
<asp:GridView ID="gvCompositeReportForAccounts" ShowFooter = "true"
runat="server" AutoGenerateColumns="False" Width="100%" CellPadding="5"
CssClass = "DataGrid"
OnRowCreated="gvCompositeReportForAccounts_RowCreated">
<Columns>
<asp:BoundField HeaderText="Sr. No.">
<ItemStyle HorizontalAlign="Center" VerticalAlign="Middle"
Width="10%" Font-Names="Sans-Serif" Font-Size="11px"
CssClass = "Item" Wrap = "false" />
<HeaderStyle HorizontalAlign="Center"
VerticalAlign="Middle" Width="10%" Font-Names="Sans-Serif"
Font-Size="11px" CssClass = "Footer" Wrap = "false" />
<FooterStyle HorizontalAlign="Center"
VerticalAlign="Middle" Width="10%" Font-Names="Sans-Serif"
Font-Size="11px" CssClass = "Footer" Wrap = "false" />
</asp:BoundField>
<asp:BoundField DataField="ProjectName" HeaderText="Project
Name">
<ItemStyle HorizontalAlign="Left" VerticalAlign="Middle"
Width="10%" Font-Names="Sans-Serif" Font-Size="11px"
CssClass = "Item" Wrap = "false" />
<HeaderStyle HorizontalAlign="Center"
VerticalAlign="Middle" Width="10%" Font-Names="Sans-Serif"
Font-Size="11px" CssClass = "Header" Wrap = "false" />
<FooterStyle HorizontalAlign="Center"
VerticalAlign="Middle" Width="10%" Font-Names="Sans-Serif"
Font-Size="11px" CssClass = "Footer" Wrap = "false" />
</asp:BoundField>
<asp:HyperLinkField DataTextField = "ProjectURL"
HeaderText="Project URL" DataNavigateUrlFields = "ProjectURL"
ControlStyle-ForeColor = "Blue">
<ItemStyle HorizontalAlign="Left" VerticalAlign="Middle"
Width="60%" Font-Names="Sans-Serif" Font-Size="11px"
CssClass = "Item" Wrap = "false" />
<HeaderStyle HorizontalAlign="Center"
VerticalAlign="Middle" Width="60%" Font-Names="Sans-Serif"
Font-Size="11px" CssClass = "Header" Wrap = "false" />
<FooterStyle HorizontalAlign="right" Font-Bold = "true"
VerticalAlign="Middle" Width="60%" Font-Names="Sans-Serif"
Font-Size="11px" CssClass = "Footer" Wrap = "false" />
</asp:HyperLinkField>
<asp:BoundField DataField="New_1" HeaderText="New">
<ItemStyle HorizontalAlign="Center" VerticalAlign="Middle"
Width="10%" Font-Names="Sans-Serif" Font-Size="11px"
CssClass = "Item" />
<HeaderStyle HorizontalAlign="Center"
VerticalAlign="Middle" Width="10%" Font-Names="Sans-Serif"
Font-Size="11px" CssClass = "Header" />
<FooterStyle HorizontalAlign="center"
VerticalAlign="Middle" Width="10%" Font-Names="Sans-Serif"
Font-Size="11px" Font-Bold = "True" CssClass = "Footer" />
</asp:BoundField>
<asp:BoundField DataField="Old_2" HeaderText="Old">
<ItemStyle HorizontalAlign="Center" VerticalAlign="Middle"
Width="10%" Font-Names="Sans-Serif" Font-Size="11px"
CssClass = "Item" />
<HeaderStyle HorizontalAlign="Center"
VerticalAlign="Middle" Width="10%" Font-Names="Sans-Serif"
Font-Size="11px" CssClass = "Header" />
<FooterStyle HorizontalAlign="center"
VerticalAlign="Middle" Width="10%" Font-Names="Sans-Serif"
Font-Size="11px" Font-Bold = "True" CssClass = "Footer" />
</asp:BoundField>
</Columns>
</asp:GridView>
Please Suggest me how should i resolve this.