Index: src/wp-admin/js/theme.js
===================================================================
--- src/wp-admin/js/theme.js	(revision 28104)
+++ src/wp-admin/js/theme.js	(working copy)
@@ -325,6 +325,7 @@
 		return $.ajax({
 			url: 'https://api.wordpress.org/themes/info/1.1/?callback=?',
 			dataType: 'jsonp',
+			timeout: 15000, // 15 seconds
 
 			// Request data
 			data: {
Index: src/wp-admin/theme-install.php
===================================================================
--- src/wp-admin/theme-install.php	(revision 28104)
+++ src/wp-admin/theme-install.php	(working copy)
@@ -56,7 +56,7 @@
 		'searchPlaceholder' => __( 'Search themes...' ), // placeholder (no ellipsis)
 		'upload' => __( 'Upload Theme' ),
 		'back'   => __( 'Back' ),
-		'error'  => ( 'There was a problem trying to load the themes. Please, try again.' ), // @todo improve
+		'error'  => __( 'An unexpected error occurred. Something may be wrong with WordPress.org. If you continue to have problems, please try the <a href="https://wordpress.org/support/">support forums</a>.' )
 	),
 	'installedThemes' => array_keys( $installed_themes ),
 	'browse' => array(