Cannot find server on Response.Redirect() to self page with querystring

 I am Redirecting to the same page on submit to avoid duplicate on page refresh.
On first submit it is fine but on second & further submit it shows "Cannot find server" after refresh evrything is fine.
Same page working fine in firefox.
 on submit

if (Insert())
{
Response.Redirect("~/AddGroup.aspx?success=1", false);
}
else
{
lblMessage.Text = "Error adding Group";
} on page loadif (Request.QueryString["success"] != null && Request.QueryString["success"].ToString() != "")
{
if (Request.QueryString["success"].ToString() == "1")
{
lblMessage. ...