JMX monitoring doesn't show any values IF jconsole as per JDK6 AND standalone instance through NA

We are facing a JMX monitoring issue with AS9.1_0x, where 'jconsole'as per a JDK6 doesn't show any attribute values, instead all attribute values are shown as "Unavailable". (see attached jconsole.png)

The issue has been isolated further. It depends on 'jconsole' as per a JDK6(tried u1 and u4). The problem does not depend on a specific setup, eg. virtual servers or so nor on a specific EAR deployed. In addition, the issue appears to happen with an instance managed through a NA only, eg. a default server instance is fine.

Note: a 'jconsole' as per a JDK5 or VisualVM does display all attribute values properly!