Error Message when downloading wordpress 3.9.1

Try downloading WordPress again and delete then replace your copies of everything except the wp-config.php file and the /wp-content/ directory with fresh copies from the download. This will effectively replace all of your core files without damaging your content and settings. Some uploaders tend to be unreliable when overwriting files, so don’t forget to delete the original files before replacing them.

It sounds like one of the core files might be corrupt, so this will both fix that and update you to 3.9.1.

Furthermore, don’t remove your database, just replace the wordpress by a new with ftp and there goes back to life.