Since upgrading from 2.5 to 2.6.1 the login page fails to redirect to the wp-admin page. If I stop the web browser and type in the full url, mysite/wp-admin/index.php all is fine.
Also the link in the sidebar to Site Admin doesn't redirect either, because the link is pointing to mysite/wp-admin and not mysite/wp-admin/index.php
Is it my Apache server or PHP that's at fault?