Sorry, should have included my code correctly:
if ($updateNode)
{
$newNode = $dom->createDocumentFragment();
//error_log("before append: ".$nodeValue);
$convertedNodeValue = str_replace('&', '&', $nodeValue); //13.12.2014 Duncan M Added otherwise 'appendXML' below was consistently failing
//error_log("after conversion: ".$convertedNodeValue);
//if (FALSE == $newNode->appendXML($nodeValue))
if (FALSE == $newNode->appendXML($convertedNodeValue))
{
error_log("WP Glossary Hover: appendXML failed, line 227 class-tooltip-parser.php");
}
$node->parentNode->replaceChild($newNode, $node);
}