Invalid Form Key. Please refresh the page / Magento admin login

If you have this issue, the method below solve it be sure =)

I had the same problem and could fix it by setting the correct web/cookie/cookie_domain and web/cookie/cookie_path values in the table core_config_data.

Don't forget to clear all session and cookie data in your browser and the Magento session and cache files/data afterwards.

Good luck!