I forgot to say one important thing: everything goes immediatly all right as soon as jboss gets restarted, so I don't think it is a net problem or something like that.
Sorry, there has been a misunderstanding..
I have already read this answer (I always look in forum for similar problem before writing anything)...but I don't think the problem is exactly the same.
The point is that my messages shouldn't expire since now I don't set time to live (it should be infinite by default).
may be a similar bug in jboss..any idea?