Regression(PIT) Test cases 4,5,and 6 fail for bug verification for 6874336 for 6u18b03

Test cases 4,5,6 from http://web-east.east.sun.com/www/tests/1.6.0_18/6874336/ fail to load the load the applet as expected.
These are java web start test cases with jar version enabled, jar pack enabled, and both jar pack and version enabled.It gives the following exception:
java.lang.IllegalStateException: DesktopBrowse instance has already been set.
at sun.awt.DesktopBrowse.setInstance(Unknown Source)
at sun.plugin2.applet.Applet2Environment.initialize(Unknown Source)
at sun.plugin2.applet.viewer.JNLP2Viewer.run(Unknown Source)
at sun.plugin2.applet.viewer.JNLP2Viewer.main(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.sun.javaws.Launcher.executeApplet(Unknown Source)
at com.sun.javaws.Launcher.executeMainClass(Unknown Source)
at com.sun.javaws.Launcher.doLaunchApp(Unknown Source)
at com.sun.javaws.Launcher.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
This behaviour is seen for both Vista,XP for both Internet Explorer and Firefox.
For 6u18b02, the same test cases give the above exception but applet gets loaded correctly.