Index: wp-admin/css/media.dev.css
===================================================================
--- wp-admin/css/media.dev.css	(revision 18736)
+++ wp-admin/css/media.dev.css	(working copy)
@@ -245,10 +245,6 @@
 	text-align: center;
 }
 
-#media-upload a.wp-post-thumbnail {
-	margin: 0 20px;
-}
-
 #media-items a.delete {
 	display: block;
 	float: right;
Index: wp-admin/includes/media.php
===================================================================
--- wp-admin/includes/media.php	(revision 18736)
+++ wp-admin/includes/media.php	(working copy)
@@ -1330,7 +1330,7 @@
 		$calling_post_id = $post->post_parent;
 	if ( 'image' == $type && $calling_post_id && current_theme_supports( 'post-thumbnails', get_post_type( $calling_post_id ) ) && get_post_thumbnail_id( $calling_post_id ) != $attachment_id ) {
 		$ajax_nonce = wp_create_nonce( "set_post_thumbnail-$calling_post_id" );
-		$thumbnail = "<a class='wp-post-thumbnail' id='wp-post-thumbnail-" . $attachment_id . "' href='#' onclick='WPSetAsThumbnail(\"$attachment_id\", \"$ajax_nonce\");return false;'>" . esc_html__( "Use as featured image" ) . "</a>";
+		$thumbnail = "<input id='wp-post-thumbnail-" . $attachment_id . "' class='button' type='submit' onclick='WPSetAsThumbnail(\"$attachment_id\", \"$ajax_nonce\");return false;' value='" . esc_attr__( "Use as featured image" ) . "' name='wp-post-thumbnail-" . $attachment_id . "' />";
 	}
 
 	if ( ( $send || $thumbnail || $delete ) && !isset( $form_fields['buttons'] ) )
Index: wp-admin/js/set-post-thumbnail.dev.js
===================================================================
--- wp-admin/js/set-post-thumbnail.dev.js	(revision 18736)
+++ wp-admin/js/set-post-thumbnail.dev.js	(working copy)
@@ -1,20 +1,20 @@
 function WPSetAsThumbnail(id, nonce){
-	var $link = jQuery('a#wp-post-thumbnail-' + id);
+	var $button = jQuery('input#wp-post-thumbnail-' + id);
 
-	$link.text( setPostThumbnailL10n.saving );
+	$button.val( setPostThumbnailL10n.saving );
 	jQuery.post(ajaxurl, {
 		action:"set-post-thumbnail", post_id: post_id, thumbnail_id: id, _ajax_nonce: nonce, cookie: encodeURIComponent(document.cookie)
 	}, function(str){
 		var win = window.dialogArguments || opener || parent || top;
-		$link.text( setPostThumbnailL10n.setThumbnail );
+		$button.val( setPostThumbnailL10n.setThumbnail );
 		if ( str == '0' ) {
 			alert( setPostThumbnailL10n.error );
 		} else {
-			jQuery('a.wp-post-thumbnail').show();
-			$link.text( setPostThumbnailL10n.done );
-			$link.fadeOut( 2000 );
+			$button.val( setPostThumbnailL10n.done );
+			$button.fadeOut( 2000 );
 			win.WPSetThumbnailID(id);
 			win.WPSetThumbnailHTML(str);
+			win.tb_remove();
 		}
 	}
 	);