A recent run of the applet compatibility test suite with the new Java Plug-In turned up the following exception for many of the applets:

java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
        at java.lang.reflect.Constructor.newInstance(Unknown Source)
        at sun.plugin2.main.client.PluginMain.createEmbeddedFrame(Unknown Source)
        at sun.plugin2.main.client.PluginMain.access$100(Unknown Source)
        at sun.plugin2.main.client.PluginMain$1.run(Unknown Source)
        at java.awt.event.InvocationEvent.dispatch(Unknown Source)
        at java.awt.EventQueue.dispatchEvent(Unknown Source)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
        at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
        at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
        at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
        at java.awt.EventDispatchThread.run(Unknown Source)
Caused by: java.lang.ClassFormatError: Incompatible magic value 1008813135 in class file default
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(Unknown Source)
        at java.security.SecureClassLoader.defineClass(Unknown Source)
        at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClassInternal(Unknown Source)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Unknown Source)
        at sun.awt.FontConfiguration$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.awt.FontConfiguration.getFontCharsetEncoder(Unknown Source)
        at sun.awt.FontConfiguration.buildFontDescriptors(Unknown Source)
        at sun.awt.FontConfiguration.getFontDescriptors(Unknown Source)
        at sun.awt.FontConfiguration.getFontDescriptors(Unknown Source)
        at sun.awt.PlatformFont.<init>(Unknown Source)
        at sun.awt.windows.WFontPeer.<init>(Unknown Source)
        at sun.awt.windows.WToolkit.getFontPeer(Unknown Source)
        at java.awt.Font.getPeer_NoClientCode(Unknown Source)
        at java.awt.Font.getPeer(Unknown Source)
        at sun.awt.windows.WComponentPeer._setFont(Native Method)
        at sun.awt.windows.WComponentPeer.setFont(Unknown Source)
        at sun.awt.windows.WWindowPeer.initialize(Unknown Source)
        at sun.awt.windows.WFramePeer.initialize(Unknown Source)
        at sun.awt.windows.WComponentPeer.<init>(Unknown Source)
        at sun.awt.windows.WCanvasPeer.<init>(Unknown Source)
        at sun.awt.windows.WPanelPeer.<init>(Unknown Source)
        at sun.awt.windows.WWindowPeer.<init>(Unknown Source)
        at sun.awt.windows.WFramePeer.<init>(Unknown Source)
        at sun.awt.windows.WEmbeddedFramePeer.<init>(Unknown Source)
        at sun.awt.windows.WToolkit.createEmbeddedFrame(Unknown Source)
        at sun.awt.windows.WEmbeddedFrame.addNotify(Unknown Source)
        at sun.awt.windows.WEmbeddedFrame.<init>(Unknown Source)
        at sun.plugin2.main.client.WPluginEmbeddedFrame.<init>(Unknown Source)
        ... 15 more

It is clear that the reason for this is that the sun.awt.FontConfiguration class is attempting to load a class called "default" and expecting to receive a ClassNotFoundException rather than a ClassFormatError. We don't know exactly what regional settings are causing this failure so we can not reproduce it in house. However the change to the code to avoid this exception is very small and straightforward.