Test JRE: b138-pit http://rehudson.sfbay.sun.com/hudsonws/deploypit/bundles/windows-i586/b255-2011-04-07_58/
Test OS: winxp, vista
Test browser: firefox 3.6.13, IE8

Steps to reproduce:
1) Launch the applet with java console open http://rehte.cn.oracle.com:8080/wshost/new_ws/deployment/src/plugin/Decoration/Decoration/html/DecorationTrueJnlp.html
2) Drag the applet out of browser. If the following exception is thrown, bug is reproduced.
Exception in thread "AWT-EventQueue-2" java.security.AccessControlException: access denied ("java.io.FilePermission" "C:\Documents and Settings\ccheung\Local Settings\Application Data\Sun\Java\Deployment\cache\6.0\lastAccessed" "read")
at java.security.AccessControlContext.checkPermission(Unknown Source)
at java.security.AccessController.checkPermission(Unknown Source)
at java.lang.SecurityManager.checkPermission(Unknown Source)
at java.lang.SecurityManager.checkRead(Unknown Source)
...
...
Exception in thread "AWT-EventQueue-2" java.awt.IllegalComponentStateException: component must be showing on the screen to determine its location
at java.awt.Component.getLocationOnScreen_NoTreeLock(Unknown Source)
at java.awt.Component.getLocationOnScreen(Unknown Source)
at com.sun.deploy.uitoolkit.impl.awt.AWTDragHelper$PerAppletInfo.refreshCloseButtonFrame(Unknown Source)
at com.sun.deploy.uitoolkit.impl.awt.AWTDragHelper$PerAppletInfo.setupCloseListener(Unknown Source)

This bug can not be reproduced always. Try a few more times.

Source code location:
http://rehte.cn.oracle.com:8080/wshost/new_ws/deployment/src/plugin/Decoration/Decoration/src