Index: modules/filter/filter.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/filter/filter.module,v
retrieving revision 1.213
diff -u -p -r1.213 filter.module
--- modules/filter/filter.module	6 May 2008 12:18:47 -0000	1.213
+++ modules/filter/filter.module	3 Jun 2008 22:48:41 -0000
@@ -751,7 +751,7 @@ function _filter_htmlcorrector($text) {
   }
 
   // Properly entify angles.
-  $text = preg_replace('!<([^a-zA-Z/])!', '&lt;\1', $text);
+  $text = preg_replace('@<([^a-zA-Z!/])@', '&lt;\1', $text);
 
   // Split tags from text.
   $split = preg_split('/<([^>]+?)>/', $text, -1, PREG_SPLIT_DELIM_CAPTURE);
@@ -786,13 +786,16 @@ function _filter_htmlcorrector($text) {
         if (count($stack) && ($stack[0] == $tagname) && isset($no_nesting[$stack[0]])) {
           $output .= '</' . array_shift($stack) . '>';
         }
-        // Push non-single-use tags onto the stack
-        if (!isset($single_use[$tagname])) {
-          array_unshift($stack, $tagname);
-        }
-        // Add trailing slash to single-use tags as per X(HT)ML.
-        else {
-          $value = rtrim($value, ' /') . ' /';
+        // Ensure we're not closing a HTML comment.
+        if ($tagname{0} != '!') {
+          // Push non-single-use tags onto the stack
+          if (!isset($single_use[$tagname])) {
+            array_unshift($stack, $tagname);
+          }
+          // Add trailing slash to single-use tags as per X(HT)ML.
+          else {
+            $value = rtrim($value, ' /') . ' /';
+          }
         }
         $output .= '<' . $value . '>';
       }