Ok, back with the results on Jboss 3.0.0 beta. The results with custom type as remote method parameter are about the same as the ones with Hashtable instead of my custom type, i.e. on average 25ms for the "invocation time".
This, however, doesn't solve my problem, as jboss 3.0.0 beta is unstable and cannot get clustering to work on it.
Does anyone know when a new version will be available ?
I tested on 2.4.4 too and the results are the same with the custom type as with the Hashtable/Vector. So it seems to be a problem only with jboss 3.0.0a.
I tested with jboss 3.0.0RC1 and this problem is no longer present. Great work guys! :)