Java 2D throws Exception when launched through browser

Tested OS : Solaris 9 sparc
Tested browser : Mozilla 1.7
Steps to reproduce :

1. Install Mozilla 1.7
2. Install Mustang build 20
3. Register mustang plugin with mozilla
4. Launch mozilla
5. Launch Java2D which is under jdk1.6.0/demo/plugin/jfc/Java2D folder
6. Click on each tab
7. Close the browser

Following message is getting displayed in the terminal

"Java process: caught exception from sun.plugin.navig.motif.Plugin.start
Exception in thread "main""

Under mozilla folder, the file named plugin_stack.trace got created with the following contents :

"java.lang.IllegalThreadStateException
        at java.lang.ThreadGroup.add(ThreadGroup.java:856)
        at java.lang.Thread.start(Thread.java:573)
        at java.lang.Shutdown.runHooks(Shutdown.java:128)
        at java.lang.Shutdown.sequence(Shutdown.java:173)
        at java.lang.Shutdown.exit(Shutdown.java:218)
        at java.lang.Runtime.exit(Runtime.java:90)
        at java.lang.System.exit(System.java:868)
        at sun.plugin.navig.motif.Plugin.doit(Plugin.java:178)
        at sun.plugin.navig.motif.Plugin.start(Plugin.java:104)"

plugin_stack.trace file attached
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