Can't Set Featured Image – Yes I Read All Other Posts

Looks like a theme-specific issue. What theme is your client using?

Item Three above. I switched to the Twenty-Eleven theme to make sure and still had the problem. The theme is a custom theme that I created myself and built on a skeleton of my own design for me to build client themes on.

This skeleton is used with at least three other sites that do NOT have this problem.

I apologize for my rather glib reply above. I started thinking about what you said and went back to my theme. I had enabled theme support in my functions file, however, I hadn’t included the code in the loop to display the thumbnail in the post if one had been set. However, when I went back to the dashboard and tried to set a thumbnail, I still got a 404 on media-upload.php:116. When I clicked on the link to that part in Chrome’s firbug window I got this code snippet:

jQuery.post(ajaxurl, {
			action:"ngg_set_post_thumbnail", post_id: post_id, thumbnail_id: id, cookie: encodeURIComponent(document.cookie)
		}, function(str){
			var win = window.dialogArguments || opener || parent || top;
			$link.text( setPostThumbnailL10n.setThumbnail );
			if ( str == '0' ) {
				alert( setPostThumbnailL10n.error );
			} else {
				jQuery('a.ngg-post-thumbnail').show();
				$link.text( setPostThumbnailL10n.done );
				$link.fadeOut( 2000 );
				// set some id as meta input filed
				win.WPSetThumbnailID('ngg-' + id);
				// replace the meta box with the image
				win.WPSetThumbnailHTML(str);
			}
		}
		);

What am I missing?

I am having the same issue with specific users. The only work around i have found is to change the users role to administrator. All of the other roles will show this same error. I am curious to hear if this solves your issue as well. Might be a bug in the user permissions.

Actually, my client and I are the only users and we are both administrators. This site is being used as a CMS only. Sorry! I wish that would help!

The second block of code that you posted above appears to be referencing a plugin – possibly NextGen.

Yes, I was trying to set the image from a NextGen gallery. Here is the block of code throwing the 404 when trying to set the image from the Media Library:

function WPSetAsThumbnail(c,b){var a=jQuery("a#wp-post-thumbnail-"+c);a.text(setPostThumbnailL10n.saving);jQuery.post(ajaxurl,{action:"set-post-thumbnail",post_id:post_id,thumbnail_id:c,_ajax_nonce:b,cookie:encodeURIComponent(document.cookie)},function(e){var d=window.dialogArguments||opener||parent||top;a.text(setPostThumbnailL10n.setThumbnail);if(e=="0"){alert(setPostThumbnailL10n.error)}else{jQuery("a.wp-post-thumbnail").show();a.text(setPostThumbnailL10n.done);a.fadeOut(2000);d.WPSetThumbnailID(c);d.WPSetThumbnailHTML(e)}})};

And when I try to upload an image and set as thumbnail:

function WPSetAsThumbnail(c,b){var a=jQuery("a#wp-post-thumbnail-"+c);a.text(setPostThumbnailL10n.saving);jQuery.post(ajaxurl,{action:"set-post-thumbnail",post_id:post_id,thumbnail_id:c,_ajax_nonce:b,cookie:encodeURIComponent(document.cookie)},function(e){var d=window.dialogArguments||opener||parent||top;a.text(setPostThumbnailL10n.setThumbnail);if(e=="0"){alert(setPostThumbnailL10n.error)}else{jQuery("a.wp-post-thumbnail").show();a.text(setPostThumbnailL10n.done);a.fadeOut(2000);d.WPSetThumbnailID(c);d.WPSetThumbnailHTML(e)}})};

You really need to post this in the NextGens’s dedicated forum (via its plugin page).

Even though I disabled that plugin and STILL couldn’t set the post thumbnail? I will, if you insist, but I really don’t think the problem is the plugin. The problem is somewhere in the admin-ajax.php function calls.

Try resetting the plugins folder by PhpMyAdmin. Sometimes, an apparently inactive plugin can still cause problems.

I just uninstalled the NextGen Gallery and optimized the database. I still get the same 404 error referencing set-post-thumbnail.js as shown above. Does that still mean that it’s the plugin causing the problem?

Did you try resetting the plugins as I suggested above?

Yes. For this domain I am webhost, webmaster and one of two administrators. I have tried ALL suggestions. The database checks okay with both wp-optimize and from the CPanel MySQL Admin / phpmyadmin.

I have WordPress 3.4.2 installed on at least eight other domains on the same server, several with the same skeletal base theme. In ALL other cases, I can set the post thumbnail and it will save properly. On THIS SITE ONLY, when I attempt to set the post thumbnail, it hangs on saving.

This is why I am so incredibly frustrated!

Site url?

salonoasis.biz