Does http://www.yoursite.com/ show as expected, but http://www.yoursite.com (without the trailing slash) redirects to http://yoursite.com (removes the www)? This behavior is a peculiar way some web servers have been misconfigured. When a web server receives a URL request that doesn't include a trailing slash, it internally interprets it as including that slash. Some web servers can be misconfigured so that they'll load it without the www. portion of the URL. This results in cookie data being lost if you don't use a .example.com cookie domain, and a possible loss of pagerank juice from links. Ask your web host to fix the problem in the web server configuration file.