When you go to http://www.site.net/wp-login.php do you get redirected to the non-www login page or does the address stay as http://www.site.net/wp-login.php
If you stay on www, you should do something about it to avoid duplicate content and other strangeness. You should redirect all www. pages to non-www pages in your DNS setup or in htaccess. How you do that depends on your web host.