The statement "new DescriptorSupport()" produces the following stack when the JMX debugging is used.
Tried JDK 6 b59g (aka Beta), b86 (aka Beta2) and b99.
All other constructors fail equally.
Works fine without any debugging.

Exception in thread "main" java.lang.IllegalArgumentException: Null Map
        at javax.management.ImmutableDescriptor.<init>(ImmutableDescriptor.java:85)
        at javax.management.modelmbean.DescriptorSupport.hashCode(DescriptorSupport.java:777)
        at javax.management.modelmbean.DescriptorSupport.debug(DescriptorSupport.java:1260)
        at javax.management.modelmbean.DescriptorSupport.debug(DescriptorSupport.java:1266)
        at javax.management.modelmbean.DescriptorSupport.<init>(DescriptorSupport.java:160)
        at defect.Main.main(Main.java:29)