Index: wp-includes/formatting.php
===================================================================
--- wp-includes/formatting.php	(revision 13536)
+++ wp-includes/formatting.php	(working copy)
@@ -1816,7 +1816,7 @@
 		$text = strip_tags($text);
 		$excerpt_length = apply_filters('excerpt_length', 55);
 		$excerpt_more = apply_filters('excerpt_more', ' ' . '[...]');
-		$words = explode(' ', $text, $excerpt_length + 1);
+		$words = preg_split("/[\n\r\t ]+/", $text, $excerpt_length + 1, PREG_SPLIT_NO_EMPTY);
 		if (count($words) > $excerpt_length) {
 			array_pop($words);
 			$text = implode(' ', $words);