Hi HuiSheng, thanks for your answer.
Yes I know that, but I don't undestand why SubProcessBinding class looks for the org/jbpm/pvm/internal/model/Activity class instead the new class. I only modified the new SubProcessActivity.java and updated SubProcessActivity.class and SubProcessBinding.class in jbpm.jar of 4.4 release.
I will try to update only SubProcessActivity.class...