problem with response.redirect

http://localhost:54495/Secure/%2fSecure%2fPrivateMessages.aspx%3ftab%3dsent


  var pm = SQLOmegaLoveProvider.InsertPrivateMessage(Convert.ToInt32(UserProfileID), Convert.ToInt32(ToUserProfileID),
                        subject, message, false, false, false, DateTime.UtcNow);
                    txtSubject.Text = "";
                    txtMessage.Text = "";
                    Response.Redirect("~/Secure/PrivateMessages.aspx?tab=sent");


                }
                        

I get the above when calling response.redirect any help would be great.
I am trying to learn from this app.