Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 19998)
+++ wp-includes/functions.php	(working copy)
@@ -2337,7 +2337,7 @@
 	 */
 	krsort($wpsmiliestrans);
 
-	$wp_smiliessearch = '/(?:\s|^)';
+	$wp_smiliessearch = '/((?:\s|^)';
 
 	$subchar = '';
 	foreach ( (array) $wpsmiliestrans as $smiley => $img ) {
@@ -2347,7 +2347,7 @@
 		// new subpattern?
 		if ($firstchar != $subchar) {
 			if ($subchar != '') {
-				$wp_smiliessearch .= ')|(?:\s|^)';
+				$wp_smiliessearch .= ')(?=\s|$))|((?:\s|^)';
 			}
 			$subchar = $firstchar;
 			$wp_smiliessearch .= preg_quote($firstchar, '/') . '(?:';
@@ -2357,7 +2357,7 @@
 		$wp_smiliessearch .= preg_quote($rest, '/');
 	}
 
-	$wp_smiliessearch .= ')(?:\s|$)/m';
+	$wp_smiliessearch .= ')(?=\s|$))/m';
 }
 
 /**