Can only use UmbracoPageResult in the context of an Http POST when using a SurfaceController form

 Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.InvalidOperationException: Can only use UmbracoPageResult in the context of an Http POST when using a SurfaceController form

The error above I got after I clicked the "register" button to submit the invalid information.

        [HttpPost]

        public ActionResult MemberRegister(MemberRegister model)

        {

            if (ModelState.IsValid)

            {

                    umMember.MemberType mt = umMember.MemberType.GetByAlias("WebsiteUser");

                    umMember.Member m = umMember.Member.MakeNew(model.UserName, mt, new umbraco.BusinessLogic.User(0));

                    m.Password = model.Password;

                    m.LoginName = model.UserName;

                    m.Email = model.Email;

                    m.XmlGenerate(new System.Xml.XmlDocument());

                    m.Save();

                ViewData.Add("Username", model.UserName);

                FormsAuthentication.SetAuthCookie(model.UserName, false);

                return RedirectToUmbracoPage(1063); //PartialView("RegSuccess");

            }

            else

            {

                return CurrentUmbracoPage();

            }

        }

It's obvious that throw this error when excute "return CurrentUmbracoPage()." I don't know how to deal with it.

hope somebody can help me. Thank you very much.