Medial Library stopped working

My library suddenly stopped during an upload, now there is an entry instead of the recent images that says:

Warning: strpos() expects parameter 1 to be string, object given in /home/…./wp-includes/post.php on line 188

Warning: preg_match() expects parameter 2 to be string, object given in /home/…../wp-includes/post.php on line 188

Catchable fatal error: Object of class WP_Error could not be converted to string in /home/……/public_html/wp-includes/post.php on line 189

The old images are still visible and the site is working properly. But when you try to use Media function there is nothing but a blank page on the Library tab.