Mnesia files migration -> ejabberd not starting

Hi all.

I'm migrating an ejabber server. I would like my users not to loose all there contacts, and informations stored by Mnesia, so I copied all /var/lib/ejabberd/spool/* files in the same directory on the new server.

When I start ejabberd from the command line, it stops here :

=PROGRESS REPORT==== 24-Jan-2007::22:45:37 ===
application: mnesia
started_at: ejabberd@server09

If I remove /var/lib/ejabberd/spool/*, then ejabberd start correctly and creates the default mnesia files.
The former ejabber server was an i386 while the new is x86_64. Even if that's not much probable, I was wondering if the mnesia files was arch dependant ?

Thanks for any help.