Since 3.5.1 I can't edit existing posts if they contain images, nor can I add images to new posts. When I click on 'Update' after editing a post, my browser gives me an error message that the web-page is unavailable "because the server where this page is located isn't responding". If the post has no images, then the update is saved.
Similarly, the Media Library displays empty, despite images having been uploaded into the correct folder (wp-content/uploads), and when I try to upload new images with the multi-file uploader, I just get the message "failed to upload due to an error -
The uploaded file could not be moved to /.../wp-content/uploads."
If I use the browser file uploader, I get this:
"Error saving media attachment".
I have gone through the troubleshooting master list, deleted all plugins, switched to the latest version of the twenty eleven theme, tried three different browsers, re-installed 3.5.1 again, pasted
define(‘CONCATENATE_SCRIPTS’, false ); into wp-config.php; tried inserting images from a URL rather than the library; all to no avail.
Any ideas what to try next?