I face a problem: I use a marker but I can't show the info window on both cases:
when a click on it,
or through setInfoWindowVisible() method
I can reproduce it on your official demo: changing tab from 'Google Maps Demo' to another one (e.g. 'Add Markers Demo') and then back again to 'Google Maps Demo', when I do click on the marker the info window does not appear again (neither the icons on the polygon).
From directory: