Index: wp-includes/formatting.php
===================================================================
--- wp-includes/formatting.php  (revision 11997)
+++ wp-includes/formatting.php  (working copy)
@@ -138,7 +138,7 @@
        $pee = $pee . "\n"; // just to make things a little easier, pad the end
        $pee = preg_replace('|<br />\s*<br />|', "\n\n", $pee);
        // Space things out a little
-       $allblocks = '(?:table|thead|tfoot|caption|col|colgroup|tbody|tr|td|th|div|dl|dd|dt|ul|ol|li|pre|select|form|map|area|blockquote|address|math|style|input|p|h[1-6]|hr)';
+       $allblocks = '(?:table|thead|tfoot|caption|col|colgroup|tbody|tr|td|th|div|dl|dd|dt|ul|ol|li|pre|select|form|fieldset|legend|map|area|blockquote|address|math|style|input|p|h[1-6]|hr)';
        $pee = preg_replace('!(<' . $allblocks . '[^>]*>)!', "\n$1", $pee);
        $pee = preg_replace('!(</' . $allblocks . '>)!', "$1\n\n", $pee);
        $pee = str_replace(array("\r\n", "\r"), "\n", $pee); // cross-platform newlines
Index: wp-admin/js/editor.dev.js
===================================================================
--- wp-admin/js/editor.dev.js   (revision 11997)
+++ wp-admin/js/editor.dev.js   (working copy)
@@ -130,7 +130,7 @@
        },
 
        wpautop : function(pee) {
-               var blocklist = 'table|thead|tfoot|caption|col|colgroup|tbody|tr|td|th|div|dl|dd|dt|ul|ol|li|pre|select|form|blockquote|address|math|p|h[1-6]';
+               var blocklist = 'table|thead|tfoot|caption|col|colgroup|tbody|tr|td|th|div|dl|dd|dt|ul|ol|li|pre|select|form|fieldset|legend|blockquote|address|math|p|h[1-6]';
 
                if ( pee.indexOf('<object') != -1 ) {
                        pee = pee.replace(/<object[\s\S]+?<\/object>/g, function(a){