On Solaris 2.6 running Netscape 4.05 with Java Plug-in 1.1.1 e (June 23rd build) you can view SwingSet at this location:
http://java.sun.com/products/plugin/1.1/demo/SwingSet/SwingSetApplet.html
However, if you click on any of the tabs you get the exceptions below, and none of the tabbed panes paint. Eventually the app hangs.

Steps to reproduce:
0) Netscape 4.05 by going to the Netscape website.
1) Install the new java plugin 1.1.1 e ( /usr/local/java/java_plug-in1.1.1/solaris/package )
2) Using the ControlPanel, have the plugin point to JDK1.2beta4-J.
3) Open this page:
http://java.sun.com/products/plugin/1.1/demo/SwingSet/SwingSetApplet.html
4) Click on the tabs.
RESULT: The following exceptions are thrown:
Exception occurred during event dispatching:
java.lang.NoSuchMethodError: com.sun.java.swing.RepaintManager: method currentManager(Lcom/sun/java/swing/JComponent;)Lcom/sun/java/swing/RepaintManager; not found
        at SwingSet$17.stateChanged(Compiled Code)
        at com.sun.java.swing.JTabbedPane.fireStateChanged(Compiled Code)
        at com.sun.java.swing.JTabbedPane$ModelListener.stateChanged(Compiled Code)
        at com.sun.java.swing.DefaultSingleSelectionModel.fireStateChanged(Compiled Code)
        at com.sun.java.swing.DefaultSingleSelectionModel.setSelectedIndex(Compiled Code)
        at com.sun.java.swing.JTabbedPane.setSelectedIndex(Compiled Code)
        at com.sun.java.swing.plaf.basic.BasicTabbedPaneUI$MouseHandler.mousePressed(Compiled Code)
        at java.awt.Component.processMouseEvent(Compiled Code)
        at java.awt.Component.processEvent(Compiled Code)
        at java.awt.Container.processEvent(Compiled Code)
        at java.awt.Component.dispatchEventImpl(Compiled Code)
        at java.awt.Container.dispatchEventImpl(Compiled Code)
        at java.awt.Component.dispatchEvent(Compiled Code)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Compiled Code)
        at java.awt.LightweightDispatcher.processMouseEvent(Compiled Code)
        at java.awt.LightweightDispatcher.dispatchEvent(Compiled Code)
        at java.awt.Container.dispatchEventImpl(Compiled Code)
        at java.awt.Component.dispatchEvent(Compiled Code)
        at java.awt.EventQueue.dispatchEvent(Compiled Code)
        at java.awt.EventDispatchThread.run(Compiled Code)