Hello Stanimir,
 Thank you for your answer. I tried your example, it worked then
added my class' logic until the error occured. I have a private
Attributes member 'attr' which is set by startElement method that I
use later with the endElement method. I know it is not safe since
'attr' is a reference on an object which can change, but this never
happened, I lazily used it like that. Obviously changes occur and only
with java 6.
I noticed that the attributes won't mute if its methods are called in
startElement. For instance, this not will work :
package javaapplication2;

import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
import org.xml.sax.helpers.XMLReaderFactory;
import java.io.*;

public class Main extends DefaultHandler {

   private Attributes attr = null;

   Main() {
   //super();
   }

   public static void main(String[] args) throws Exception {
       InputSource input = new InputSource(new
FileReader("test.xml"));
       XMLReader xr = XMLReaderFactory.createXMLReader();
       DefaultHandler handler = new Main();
       xr.setContentHandler(handler);
       xr.setErrorHandler(handler);
       xr.parse(input);
   }

   public void startElement(String uri, String localName,
           String qname, Attributes atts) {
//        System.out.print("<" + qname);
//        for (int i = 0,  len = atts.getLength(); i < len; i++) {
//            System.out.print(" " + atts.getQName(i) + "=\"" +
atts.getValue(i) + "\"");
//        }
//        System.out.println(">");
       indent++;
       this.attr = atts;
   }

   public void endElement(String uri, String localName,
           String name) {
       indent--;

       if (localName.equals("re")) {
           String calcAttr = attr.getValue("v");
           int calcValue = 0;
           if (calcAttr != null) {
               // Here is the where the exception is raised,
calcAttr's value is '<' although there is NO such attribute
               calcValue = Integer.parseInt(calcAttr);
           }
           return;
       }
   }
   private int indent;
}
Ant this will work, the difference is that methods of 'atts' are
called :
package javaapplication2;

import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
import org.xml.sax.helpers.XMLReaderFactory;
import java.io.*;

public class Main extends DefaultHandler {

   private Attributes attr = null;

   Main() {
   //super();
   }

   public static void main(String[] args) throws Exception {
       InputSource input = new InputSource(new
FileReader("test.xml"));
       XMLReader xr = XMLReaderFactory.createXMLReader();
       DefaultHandler handler = new Main();
       xr.setContentHandler(handler);
       xr.setErrorHandler(handler);
       xr.parse(input);
   }

   public void startElement(String uri, String localName,
           String qname, Attributes atts) {
       System.out.print("<" + qname);
       for (int i = 0,  len = atts.getLength(); i < len; i++) {
           System.out.print(" " + atts.getQName(i) + "=\"" +
atts.getValue(i) + "\"");
       }
       System.out.println(">");
       indent++;
       this.attr = atts;
   }

   public void endElement(String uri, String localName,
           String name) {
       indent--;

       if (localName.equals("re")) {
           String calcAttr = attr.getValue("v");
           int calcValue = 0;
           if (calcAttr != null) {
               // Here is the where the exception is raised,
calcAttr's value is '<' although there is NO such attribute
               calcValue = Integer.parseInt(calcAttr);
           }
           return;
       }
   }
   private int indent;
}
 I recognize that I did something dangerous, but no accident happened
with java 6.
 Small question : why don't you call the superclass' constructor in
your example ?
 Thanks again Stanimir,
Ghislain