In June, Google Maps introduced a new style of smart navigation in
Street View that allows users to double-click on areas of the panorama
in order to navigate to them. We will be enabling this navigation in
the GStreetviewPanorama class in the API in several weeks (likely
version 2.174). We do not expect that this change will break any
sites, but if you are heavily using GStreetviewPanorama on your site,
you may want to check your site behaves as expected once the change is
live.
You can read more about the smart navigation in this blog post:
http://google-latlong.blogspot.com/2009/06/introducing-smart-navigation-in-street.html