A DESCRIPTION OF THE PROBLEM :
A call to org.w3c.dom.Element.setAttributeNS(aNamespace, "aName","aValue") unsets an existing attribute not named "aName".

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the sample

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
This output:
Variant 0 using name "location" tested OK.
Variant 1 using name "location" tested OK
Variant 2 using name "location" tested OK
Variant 0 using name "ns0:location" tested OK
Variant 1 using name "ns0:location" tested OK
Variant 2 using name "ns0:location" tested OK
Variant 0 using name "info:location" tested OK.
Variant 1 using name "info:location" tested OK
Variant 2 using name "info:location" tested OK
ACTUAL -
This output:
Variant 0 using name "location" failed.
Variant 1 using name "location" tested OK
Variant 2 using name "location" tested OK
Variant 0 using name "ns0:location" tested OK
Variant 1 using name "ns0:location" tested OK
Variant 2 using name "ns0:location" tested OK
Variant 0 using name "info:location" failed.
Variant 1 using name "info:location" tested OK
Variant 2 using name "info:location" tested OK

---------- BEGIN SOURCE ----------
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.w3c.dom.DOMImplementation;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.StringReader;
import java.net.URL;
/**
 * Calling calling org.w3c.dom.Element.setAttributeNS(ANamespace,"aLocalNameOtherThanName",aValue) can have the side effect of removing the "name" attribute from that node.
 * Test show show that the behavior can depend on:
 * - the number of attributes (removing any one of the 5 attributes will no longer reproduce the issue)
 * - the alphabetic order of the attributes (changing the name of the first from "a" to "w" or of the last from "o" to "n" will no longer reproduce the issue)
 */
public class DomBug
{
    static final String NS="http://www.foo.com/LOCATION";
    public static void main(String[] args) throws Exception
    {
        test(0,"location"); //fails
        test(1,"location"); //OK
        test(2,"location"); //OK

        test(0,"ns0:location"); //OK
        test(1,"ns0:location"); //OK
        test(2,"ns0:location"); //OK

        test(0,"info:location"); //fails
        test(1,"info:location"); //OK
        test(2,"info:location"); //OK
    }
    static void test(int variant,String qName) throws Exception
    {
        Element e=getElement(variant);

        assert e.hasAttribute("name");
        e.setAttributeNS(NS,qName,"y");
        if(!e.hasAttribute("name"))
            System.err.println("Variant "+variant+" using name \""+qName+"\" failed.");
        else
            System.out.println("Variant "+variant+" using name \""+qName+"\" tested OK");
    }
    static Element getElement(int variant) throws Exception
    {
        DocumentBuilderFactory documentBuilderFactory=DocumentBuilderFactory.newInstance();
        documentBuilderFactory.setNamespaceAware(true);
        DocumentBuilder documentBuilder=documentBuilderFactory.newDocumentBuilder();
        Document document=documentBuilder.parse(new InputSource(new StringReader(
        "<?xml version='1.0'?>\n"+
        "<other:Root xmlns:other='http://www.foo.com/OTHER&#39; xmlns='http://www.foo.com/DEFAULT&#39; xmlns:ns0='http://www.foo.com/LOCATION&#39;>\n"+
        (variant==0?
        " <ANODE a='a' b='b' c='c' name='AName' ns0:location='x' o='o'/>\n"
         :variant==1?
        " <ANODE w='w' b='b' c='c' name='AName' ns0:location='x' o='o'/>\n"
         :
        " <ANODE a='a' b='b' c='c' name='AName' ns0:location='x' n='n'/>\n"
        )+
        "</other:Root>"
        )));
        return (Element)document.getElementsByTagName("ANODE").item(0);
    }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
In the call to org.w3c.dom.Element.setAttributeNS() use the same prefix in the qualified name that is specified in the original document.