blank page

i’ m using wordpress in a shelf-hosted server for a month ago. yesterday something happen and now i have no front-end page or my dashboard. i have no ability to control my site
trying to manually install the latest version put new wp-admin and wp-include, overwrite wp-content but nothing happens
i believe that my problem causes after trying to install some plugins ?
any help
front page http://www.fsk.gr
dashboard http://www.fsk.gr/wordpress/wp-admin