Deleting Widgets

I've managed to narrow down the problem and it seems to just be affecting the native ui datapicker.

The code below has a stackscreen with 2 screens, when you click the button to go from the first to the second screen it deletes whatever widgets are in the layout so they can be replaced.  The button is replaced succesfully but the creation of a new date picker seems to cause problems - i create and delete the datepicker at the same time because it seems to prove there is something wrong with the declaration without having to add it to any layouts.  This does seem to be related in some way to the layout that is defined underneath - if you move the datepicker declaration and delete to after the layout  declaration, then everything seems to work fine.  If i put in any other type of widget instead of a datepicker then it works fine.  It doesnt seem to matter if its a layout as the second widget or something else - i tested with a button.

This does seem to be a rather specialised issue but i'm worried that it is a manifestation of something more major.

Thanks

#include <ma.h>                 // Syscalls
#include <MAUtil/String.h>        // C++ String class
#include <MAUtil/Moblet.h>        // Moblet class
#include <conprint.h>            // lprintfln for logging

#include <NativeUI/Widget.h>
#include <NativeUI/Widgets.h>// Include all widgets

using namespace MAUtil;
using namespace NativeUI;

class NativeUIMoblet : public Moblet, public ButtonListener {
public:

    NativeUIMoblet()
    {
        stack = new StackScreen();

        screen1 = new Screen();
        button1 = new Button();
        button1->setText("button1");
        button1->addButtonListener(this);
        screen1->setMainWidget(button1);

        screen2 = new Screen();
        button2 = new Button();
        button2->setText("back");
        button2->addButtonListener(this);

        VerticalLayout* layout = new VerticalLayout();

        mainLayout = new VerticalLayout();
        mainLayout->wrapContentVertically();
        mainLayout->addChild(button2);
        mainLayout->addChild(layout);
        screen2->setMainWidget(mainLayout);

        stack->push(screen1);
        stack->show();
    }

    void NativeUIMoblet::buttonClicked(Widget* button) {
        if(button == button2) {
            stack->pop();
        }
        else {
            int widgets = mainLayout->countChildWidgets();

            for(int i=0; i<widgets; i++) {
                Widget* temp = mainLayout->getChild(0);
                mainLayout->removeChild(temp);
                delete temp;
            }

            button2 = new Button();
            button2->setText("back");
            button2->addButtonListener(this);

            DatePicker* date = new DatePicker();
            delete date;
            date = NULL;

            VerticalLayout* layout = new VerticalLayout();

            mainLayout->addChild(button2);
            mainLayout->addChild(layout);

            stack->push(screen2);
        }
    }

    virtual ~NativeUIMoblet(){}

private:
    Screen* screen1;
    Screen* screen2;
    Button* button1;
    Button* button2;
    StackScreen* stack;
    VerticalLayout* mainLayout;
};

extern "C" int MAMain(){
    NativeUIMoblet* moblet = new NativeUIMoblet();
    Moblet::run(moblet);
    delete moblet;
    return 0;
}

But i'm building for iphone, not android (i think i failed to mention that earlier)