Google maps - G_HYBRID_MAP undefined error

Question

I'm getting an intermittent problem with a google map (api v2) - "Error: 'G_HYBRID_MAP' is undefined". I'm trying to reference that variable in a function that is called on the document ready event, via jquery, i.e.

<script src="http://maps.google.com/maps?file=api&amp;v=2&amp;key=[key]&amp;sensor=false"
        type="text/javascript"></script>

<script type="text/javascript">
function init() {
    var mapType = G_HYBRID_MAP;
}

$(document).ready(function()
    init();
});
</script>

Using firebug, I've determined that variables defined in the google map javascript are available:

>>> G_INCOMPAT
false

but:

>>> G_HYBRID_MAP
TypeError: 'G_HYBRID_MAP' is undefined

Does anyone know what file defines G_HYBRID_MAP and how the google code imports that? Any ideas why that import might be failing?