Magento – Invalid Form Key. Please refresh the page

There is one more source for this error: a wrong cookie_domain in the configuration. As you can't login into the admin area, you can check it directly via mysql:

SELECT * FROM core_config_data WHERE path LIKE '%cookie_domain%';

You can change the value in mysql directly as well. Don't forget to clear the cache afterwards.

Such issues comes due to cookies or cache problem. Delete cache from your magento_root/var/cache and remove cookies from your browser. One more reason may be incorrect data in web/cookie/cookie_domain and web/cookie/cookie_path values in core_config_data table.