Using phpMyAdmin, in your magento database, look for the core_config_data table and click it. Click the "Search" tab. Then on the "path" column set the operator to LIKE %...% and the Value to cookie and click the "Go" button to search.
After searching, set the value of web/cookie/cookie_path, web/cookie/cookie_domain, web/cookie/cookie_httponly, and web/browser_capabilities/cookies to NULL
Just like this on the screenshot.
Adding product to cart and logging in to the admin panel should work now!