java.util.ConcurrentModificationException when launching aa signed applet .

I am getting the following error while trying to launch a signed applet with JRE 1.6.0_01. It works fine on most of the machines. Any help, advise is appreciated.Thanks
[189 byte] By [rp123a] at [2007-11-27 5:18:21]
# 1

Did not include the full stack trace, here it is:

ava.util.ConcurrentModificationException

at java.util.AbstractList$Itr.checkForComodification(Unknown Source)

at java.util.AbstractList$Itr.next(Unknown Source)

at com.sun.deploy.security.WIExplorerCertStore.getCertificates(Unknown Source)

at com.sun.deploy.security.TrustDecider.isAllPermissionGranted(Unknown Source)

at com.sun.deploy.security.TrustDecider.isAllPermissionGranted(Unknown Source)

at sun.plugin.security.PluginClassLoader.getPermissions(Unknown Source)

at java.security.SecureClassLoader.getProtectionDomain(Unknown Source)

at java.security.SecureClassLoader.defineClass(Unknown Source)

at java.net.URLClassLoader.defineClass(Unknown Source)

at java.net.URLClassLoader.access$000(Unknown Source)

at java.net.URLClassLoader$1.run(Unknown Source)

at java.security.AccessController.doPrivileged(Native Method)

at java.net.URLClassLoader.findClass(Unknown Source)

at sun.applet.AppletClassLoader.findClass(Unknown Source)

at java.lang.ClassLoader.loadClass(Unknown Source)

at sun.applet.AppletClassLoader.loadClass(Unknown Source)

at java.lang.ClassLoader.loadClass(Unknown Source)

at sun.applet.AppletClassLoader.loadCode(Unknown Source)

at sun.applet.AppletPanel.createApplet(Unknown Source)

at sun.plugin.AppletViewer.createApplet(Unknown Source)

at sun.applet.AppletPanel.runLoader(Unknown Source)

at sun.applet.AppletPanel.run(Unknown Source)

at java.lang.Thread.run(Unknown Source)

rp123a at 2007-7-12 10:41:29 > top of Java-index,Security,Signed Applets...