I don't think that there is anything wrong with the return status - it is just an empty message.
If you look at the Results when you start/stop an Application from inside the admin-console, you'll see this line: "The operation did not return any results."
You'll not be able to see that the Application has been stopped in admin-console, when started/stopped from the jmx-console web page
(what twiddle also is using).
The two 'admin' web pages admin-console and jmx-console are working independently of each other.
The still new admin-console is using SEAM to control the 'jobs', and the 'old' jmx-console is using .... JMX.
As far as I know there doesn't exist a command line tool
(not yet??) for the admin-console.
In jmx-console you'll start/stop your web Applications under "jboss.web.deployment" - but monitor if they are available under "jboss.web"
(this is the way I'm able to do it).
When you stop your Application it is undeployed, and removed from the "jboss.web" view - but not removed from the deploy folder - and when you start your Application it is deployed, and added to the "jboss.web" view again.
In the
JBoss AS console (or log) you'll see the output from both the admin-console and the jmx-console.