OK thanks Bitt. This is what I'm getting, but it doesn't mean a hell of a lot to me although a null pointer is obviously a bad thing:

C:\Program Files\Java\jre1.5.0_06\bin>java.exe -jar jemplode.jar
java.lang.NullPointerException
at com.sun.java.swing.plaf.windows.XPStyle.getString(Unknown Source)
at com.sun.java.swing.plaf.windows.XPStyle.getString(Unknown Source)
at com.sun.java.swing.plaf.windows.XPStyle.<init>(Unknown Source)
at com.sun.java.swing.plaf.windows.XPStyle.getXP(Unknown Source)
at com.sun.java.swing.plaf.windows.WindowsTreeUI$ExpandedIcon.<init>(Unknown Source)
at com.sun.java.swing.plaf.windows.WindowsTreeUI$ExpandedIcon.createExpandedIcon(Unknown Source)
at com.sun.java.swing.plaf.windows.WindowsLookAndFeel.initComponentDefaults(Unknown Source)
at javax.swing.plaf.basic.BasicLookAndFeel.getDefaults(Unknown Source)
at javax.swing.UIManager.setLookAndFeel(Unknown Source)
at javax.swing.UIManager.setLookAndFeel(Unknown Source)
at org.jempeg.empeg.manager.EmplodeUI.<init>(EmplodeUI.java:204)
at org.jempeg.empeg.manager.Main.start(Main.java:83)
at org.jempeg.empeg.manager.Main.main(Main.java:133)

Exception in thread "main" java.lang.NullPointerException
at javax.swing.MultiUIDefaults.getUIError(Unknown Source)
at javax.swing.UIDefaults.getUI(Unknown Source)
at javax.swing.UIManager.getUI(Unknown Source)
at javax.swing.JPanel.updateUI(Unknown Source)
at javax.swing.JPanel.<init>(Unknown Source)
at javax.swing.JPanel.<init>(Unknown Source)
at javax.swing.JPanel.<init>(Unknown Source)
at javax.swing.JRootPane.createGlassPane(Unknown Source)
at javax.swing.JRootPane.<init>(Unknown Source)
at javax.swing.JFrame.createRootPane(Unknown Source)
at javax.swing.JFrame.frameInit(Unknown Source)
at javax.swing.JFrame.<init>(Unknown Source)
at org.jempeg.empeg.manager.EmplodeUI.<init>(EmplodeUI.java:214)
at org.jempeg.empeg.manager.Main.start(Main.java:83)
at org.jempeg.empeg.manager.Main.main(Main.java:133)