Error message

Can we see the full error message please?

That’s only half of the error message. We need to see the full error message.

So you are not running WordPress 3.6 as you indicated when starting this topic? In that case, what version of WordPress are you currently running?

Start by re-uploading all files & folders – except the root wp-config.php & .htaccess files and the the wp-content folder – from a fresh download of WordPress 3.5.1. Make sure that you delete the old copies of files & folder before uploading the new ones.

Please see the link I posted above.