FULL PRODUCT VERSION :
java version "1.6.0-rc"
Java(TM) SE Runtime Environment (build 1.6.0-rc-b101)
Java HotSpot(TM) Client VM (build 1.6.0-rc-b101, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Linux 2.6.16.13-4-default
SUSE Linux 10.1, SUSE Linux Enterprise Desktop.
KDE 3.5.1 to 3.5.5

A DESCRIPTION OF THE PROBLEM :
When try to invoke any sort of operation from java.awt.Desktop - it throws IOException. tested on about 8 SUSE boxes with KDE enviroment. didnt tested on other desktops.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. create test class with NetBeans
2. compile.
3. run.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
invocation of browser, mailer, default application.
ACTUAL -
IOException

ERROR MESSAGES/STACK TRACES THAT OCCUR :
java.io.IOException: Failed to show URI:mailto:###@###.###
        at sun.awt.X11.XDesktopPeer.launch(XDesktopPeer.java:75)
        at sun.awt.X11.XDesktopPeer.mail(XDesktopPeer.java:60)
        at java.awt.Desktop.mail(Desktop.java:456)
        at DesktopTest$1.actionPerformed(DesktopTest.java:20)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
        at java.awt.Component.processMouseEvent(Component.java:6038)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3260)
        at java.awt.Component.processEvent(Component.java:5803)
        at java.awt.Container.processEvent(Container.java:2058)
        at java.awt.Component.dispatchEventImpl(Component.java:4410)
        at java.awt.Container.dispatchEventImpl(Container.java:2116)
        at java.awt.Component.dispatchEvent(Component.java:4240)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3986)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916)
        at java.awt.Container.dispatchEventImpl(Container.java:2102)
        at java.awt.Window.dispatchEventImpl(Window.java:2429)
        at java.awt.Component.dispatchEvent(Component.java:4240)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.Desktop;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.net.URI;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class DesktopTest {
    
    public DesktopTest() {
        JPanel panel = new JPanel();
        
        if (Desktop.isDesktopSupported()) {
            JButton reportButton = new JButton("compose mail!");
            reportButton.addActionListener(new ActionListener() {
                public void actionPerformed(ActionEvent ev) {
                    try {
                        Desktop.getDesktop().mail(new URI("mailto", "###@###.###", null));
                    } catch (Exception ex) {
                        ex.printStackTrace();
                    }
                }
            });
            panel.add(reportButton);
        }
        panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
        
        
        JFrame frame = new JFrame();
        frame.setContentPane(panel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
    }
    
    public static void main(String[] args) {
        new DesktopTest();
    }
    
}

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