Problem with contact groups

With our migration (zxbackup 1.6.3 on both servers and Zimbra NE 7.1.2 to Zimbra FOSS 8.0.1) have detected a small problem with the contacts.

Not imported any contact group, and users complain too much ... : (

We tried to import an export made ​​in user preferences with version 7 and fails too! This import process says "Finished successfully" but do not import any group. Also do not know if it is related to zimbra 8 or zextras ...

Anyone else has happened?

Thanks in advance...
Sergi