I've the same problem
il migratione wizard log i see:
17-10-2006 14:39:46 : Work arrived.../o=GME/ou=First Administrative Group/cn=Recipients/cn=cost email@example.com
17-10-2006 14:39:46 : Logging on to zimbra server (192.168.100.9:7071)
17-10-2006 14:40:10 : RPC Error: Unable to connect.
17-10-2006 14:40:10 : Waiting for work
17-10-2006 14:40:10 : Worker thread exiting
the ssl certificate is sel signed by zimbra.
I can login to admin interface with firefox on the same addres
I use in the migration tool.
Can I chek any log on the server?