David Jennaway has a great article on the CRM community site that discuss when the default organization is not the default organization. This is something that a number of CRM users get confused about and David does a great job of explaining how this works. Read the article at
http://community.dynamics.com/product/crm/crmtechnical/b/crmdavidjennaway/archive/2010/11/11/when-is-the-default-organisation-not-the-default-organisation.aspx
