Ok it seems you are talking about single product page.
This can be due to plugin conflict on your site so please try temporary deactivating all plugins except woocommerce & unyson plugins and see whether everything works fine and then enable the plugins one by one to see which plugin is conflicting if any.
Also please try resetting your htaccess file as described on the following pages.
http://www.bordercrossingmedia.com/2009/01/how-to-restore-your-wordpress-htaccess-file/