MembershipProvider custom - Error on saving using EF POCO 4.1

I'm customizing the class MembershipProvider.

When navigating to Asp.net Web Site Administration Tool can list the users normally.

The code below is responsible for entering the user in the database:

public User CreateUser(string username, string password, string email)
{
    using (var db = new DataContext())
    {
        var user = new User
                        {
                            Name = username
                            ,
                            Password = password
                            ,
                            Gender = Gender.Unknown
                            ,
                            IsApproved = false
                            ,
                            IsBlock = false
                        };

        db.Users.Add(user);

        db.SaveChanges();
        return GetUser(username);
    }
}

Error on line db.SaveChanges();

When trying to register a new user, the following error appears:

**Error on Asp.net Administration Tool **

The following message may help in diagnosing the problem: Exception has been thrown by the target of an invocation. at System.RuntimeMethodHandle._InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeType typeOwner) at System.RuntimeMethodHandle.InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeType typeOwner) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) at System.Web.Administration.WebAdminMembershipProvider.CallWebAdminMembershipProviderHelperMethodOutParams(String methodName, Object[] parameters, Type[] paramTypes) at System.Web.Administration.WebAdminMembershipProvider.CreateUser(String username, String password, String email, String passwordQuestion, String passwordAnswer, Boolean isApproved, Object providerUserKey, MembershipCreateStatus& status) at System.Web.UI.WebControls.CreateUserWizard.AttemptCreateUser() at System.Web.UI.WebControls.CreateUserWizard.OnNextButtonClick(WizardNavigationEventArgs e) at System.Web.UI.WebControls.Wizard.OnBubbleEvent(Object source, EventArgs e) at System.Web.UI.WebControls.CreateUserWizard.OnBubbleEvent(Object source, EventArgs e) at System.Web.UI.WebControls.Wizard.WizardChildTable.OnBubbleEvent(Object source, EventArgs args) at System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) at System.Web.UI.WebControls.Button.OnCommand(CommandEventArgs e) at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

Erro on EventViewer

Exception information: 
    Exception type: TargetInvocationException 
    Exception message: Exception has been thrown by the target of an invocation.
   at System.RuntimeMethodHandle._InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
   at System.RuntimeMethodHandle.InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Web.Administration.WebAdminMembershipProvider.CallWebAdminMembershipProviderHelperMethodOutParams(String methodName, Object[] parameters, Type[] paramTypes)
   at System.Web.Administration.WebAdminMembershipProvider.CreateUser(String username, String password, String email, String passwordQuestion, String passwordAnswer, Boolean isApproved, Object providerUserKey, MembershipCreateStatus& status)
   at System.Web.UI.WebControls.CreateUserWizard.AttemptCreateUser()
   at System.Web.UI.WebControls.CreateUserWizard.OnNextButtonClick(WizardNavigationEventArgs e)
   at System.Web.UI.WebControls.Wizard.OnBubbleEvent(Object source, EventArgs e)
   at System.Web.UI.WebControls.CreateUserWizard.OnBubbleEvent(Object source, EventArgs e)
   at System.Web.UI.WebControls.Wizard.WizardChildTable.OnBubbleEvent(Object source, EventArgs args)
   at System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args)
   at System.Web.UI.WebControls.Button.OnCommand(CommandEventArgs e)
   at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument)
   at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)
   at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)
   at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

Type is not resolved for member 'System.Data.Entity.Infrastructure.DbUpdateException+DbUpdateExceptionState,EntityFramework, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.
   at System.Web.Administration.WebAdminConfigurationHelper.CallMembershipProviderMethod(String methodName, Object[] parameters, Type[] paramTypes)

I managed to solve. The error was in the InnerException property. The problem was a date format only;