green thumb is probably refreshing your screen because something is throwing a javascript error somewhere -- clicking the thumb is like clicking a normal link, but that link triggers an ajax request to the server and then javascript has to tell your browser "Dont follow the link, it was being used for something else, so just ignore the click". But if there was an error beforehand, javascript will just die and not work anymore, and the click goes through like a normal click.
Things that could be causing javascript errors are fishy looking toolbars, or browser addons.
