FULL PRODUCT VERSION :
JRE version 1.6.0_07 Java HotSpot(TM) Client VM

ADDITIONAL OS VERSION INFORMATION :
Windows XP

EXTRA RELEVANT SYSTEM CONFIGURATION :
Java Web Start 1.6.0_07

A DESCRIPTION OF THE PROBLEM :
We use Java Web Start  and -Dsun.lang.ClassLoader.allowArraySyntax=true(This property is needed to woraround for the bug 6434149  for JAVA 1.6 ) as it won't work without it.
The local client version of the application works perfectly with the property set to true as a JAVA option.
This  "sun.lang.ClassLoader.allowArraySyntax" property doesn't belong to the list of secure properties that can be passed into a Webstart application using the java-vm-args attribute. So that Webstart apps could not get around the issue like this:

<j2se version="1.6.0_05+"
          java-vm-args="-Dsun.lang.ClassLoader.allowArraySyntax=true" ...

sun.lang.ClassLoader.allowArraySyntax is not included in this list of secure properties for Java 1.6: http://java.sun.com/javase/6/docs/technotes/guides/javaws/developersguide/syntax.html#resources  .

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
In a JNLP file(.jsp) used for launcing the webstart pass the follwoing:
<j2se version="1.6.0_05+"
          java-vm-args="-Dsun.lang.ClassLoader.allowArraySyntax=true">
as part of <resources>.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The webstart JAVA debug console doesnt show the property Dsun.lang.ClassLoader.allowArraySyntax=true from being passed to the VM. This shows that the properoty is filtered out.
ACTUAL -
The property is not filterered out when passed into as java-vm-args value.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Caused by: java.lang.ClassNotFoundException: Classloader  <x> is not registered.  Object of type ....cannot be deserialized from loader
[Ljava.lang.String;
        at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
        at test.main(test.java:7)


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
public class test {

      public static void main(String[] args) throws Exception {

          String[] s = new String[] { "123" };
          String clName = s.getClass().getName();
          test.class.getClassLoader().loadClass(clName);
      }
  }

This runs fine on JDK 1.5, but throws this exception on JDK 6.0:

Exception in thread "main" java.lang.ClassNotFoundException: [Ljava.lang.String;
        at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
        at test.main(test.java:7)

pasted from Sun bug i.d : 6434149 .

---------- END SOURCE ----------