I am using Swing-0.4 on JDK1.1.4.
steps to reproduce:
1) launch swing demo Stylepad
2) hightlight a paragraph
3) Edit->Cut
4) The Exception thrown

Here is the stack trace:
-------------------------
Exception occurred during event dispatching:
java.lang.NullPointerException
at com.sun.java.swing.text.DefaultStyledDocument$ElementBuffer.canJoin(DefaultStyledDocument.java:885)
at com.sun.java.swing.text.DefaultStyledDocument$ElementBuffer.removeElements(DefaultStyledDocument.java:862)
at com.sun.java.swing.text.DefaultStyledDocument$ElementBuffer.removeElements(DefaultStyledDocument.java:844)
at com.sun.java.swing.text.DefaultStyledDocument$ElementBuffer.removeUpdate(DefaultStyledDocument.java:630)
at com.sun.java.swing.text.DefaultStyledDocument$ElementBuffer.remove(DefaultStyledDocument.java:586)
at com.sun.java.swing.text.DefaultStyledDocument.removeUpdate(DefaultStyledDocument.java:384)
at com.sun.java.swing.text.AbstractDocument.remove(AbstractDocument.java:144)
at com.sun.java.swing.text.JTextComponent.cut(JTextComponent.java:223)
at com.sun.java.swing.text.JTextComponent$CutAction.actionPerformed(JTextComponent.java:963)
at com.sun.java.swing.AbstractButton$2.actionPerformed(AbstractButton.java:579)
at com.sun.java.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:222)
at com.sun.java.swing.AbstractButton.doClick(AbstractButton.java:130)
at com.sun.java.swing.basic.BasicMenuUI$MenuListener.mouseReleased(BasicMenuUI.java:176)
at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:236)
at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:235)
at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:235)
at java.awt.Component.processMouseEvent(Component.java:2284)
at java.awt.Component.processEvent(Component.java:2129)
at java.awt.Container.processEvent(Container.java:890)
at java.awt.Component.dispatchEventImpl(Component.java:1764)
at java.awt.Container.dispatchEventImpl(Container.java:935)
at java.awt.Component.dispatchEvent(Component.java:1704)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:1539)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:1448)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:1383)
at java.awt.Container.dispatchEventImpl(Container.java:922)
at java.awt.Window.dispatchEventImpl(Window.java:443)
at java.awt.Component.dispatchEvent(Component.java:1704)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:63)