Description:
------------
Hopefully this is something that's fairly easy to see in the code. Providing a 
full working code sample will be somewhat difficult. This seems to happen most 
frequently with nodes that have been removed from the dom and added back 
elsewhere.

Basically if I call lookupNamespace on a node I'm getting nothing back. If I load 
the node into SimpleXML and call getNamespaces I'm getting the namespace as 
expected.

The attached code is a workaround for the problem.

Test script:
---------------
  private function get_namespace($node) {
        $node_namespace = $node->lookupNamespaceURI($node->prefix);
        if($node instanceof DomElement && $node_namespace == null && strpos($node->nodeName, ":") !== false) {
            // must be some sort of DOM bug. Look and see if we can figure it out from simplexml
            $sxe = simplexml_import_dom($node);
            $namespaces = $sxe->getNamespaces();
            foreach($namespaces as $prefix => $namespace) {
                if(strpos($node->nodeName, $prefix . ":") == 0) {
                    $node_namespace = $namespace;
                    break;
                }
            }
        }
        return $nodeNamespace;
    }


Expected result:
----------------
I expect that if I get into the body of the if statement that I will return a 
null $node_namespace. Preferably I'd never get into the if statement.