Reproducible crash Win 2K, 0.5.1 php 4.2.0

I have written a small application to load glade files and insert their contents into a notebook in my main application window. To do this i create a glade file as normal, then edit the glade file manually, removing the header (project directory etc) and the main window widget (so that the glade file only contains the top level widget, a GtkBox or Table) I name the top level widget app_main. I then load this file into my application like this... function load_app($appname, $label_text='New App'){

    $appgx =& new GladeXML("glx/$appname/$appname.glade");
    $app = $appgx->get_widget('app_main');
    $label =& new GtkLabel($label_text);
    $this->nb->prepend_page($app, $label);
    $this->nb->set_page(0);
    unset($appgx);
    unset($app);
    }

This works as expected the first time, but crashes the second time round, where it should load another application into a new notebook tab. I have tested it using 2 (hacked) glade files and it still produces the error on the second time, which ever file i load in. Please contact me directly and I can send you a zip with the files needed. Mike