jquery - custom bind events error in FF

Question

Morning, I have an error appearing in firfox:

TypeError: handlers.push is not a function handlers.push( handleObj );

The error is caused from binding to a custom event

_submit.bind('watch.changed', function () {
    var $ob = $(this);
    if ($ob.attr('disabled') && $ob.attr('disabled') === 'disabled') {
        $tmp.attr('disabled', 'disabled').addClass('disabled');
    } else {
        $tmp.removeAttr('disabled').removeClass('disabled');
    }
});

Has anyone come accros this or know of a way around it?

regards