[mdr-users] Clean up...

Hi.
I have a problem with my XMI importer. The first time I run it, it
works fine, but the second run in the same process duplicates all
components.
I want to reset the Repository each time I run my method.
I tried this methods:
        MDRManager.getDefault().shutdownAll();
        MDRepository rep=
MDRManager.getDefault().getDefaultRepository().shutdown();
but them, i'm unable to run again, it gives me exceptions until I
restart my program.
Any tips? some command to clean an extend or model ?
I tried too to clean the contents of the model by using the clear
command in the ref collections, but they are read only.

Thanks