Double click a message from a ajax folder view. The message is displayed (in my case with a new window). choose with a click the "Delete" action (from close/print/delete/reply/etc).
Delete does no delete the message. no effect.
We just upgraded to 6.0.4 and see this now.
Does anyone else see this as a problem?
(or does it work for you?)

I think this may be bugreport worthy.