The latest version of the Maps JavaScript solves this issue (the culprit is the getSearchOrigin function in Maps.js).
You can get the latest version of Maps.js from a Dynamicweb Application package [http://developer.dynamicweb-cms.com/downloads/dynamicweb-8.aspx]. Extract the file Admin/Update/Files/Templates/Maps/javascripts/Maps.js from the archive and replace your old copy.