WordPress redirect loop on wp-admin
If you change the site URL in WP, it’s possible to lock yourself out of the admin site by virtue of a redirect loop.
If you’ve got access to the database, you can revert that change. If not…
You can update wp-config.php to override those settings; WP_HOME and WP_SITEURL.
http://codex.wordpress.org/Changing_The_Site_URL