I have the same problem here... i'm trying to migrate one domain from Plesk 8.6 (it's on our dedicated server, all domains are under one "client") to Plesk 10.4.4 (another vps server: on this for each domain, we will create a "client")
The error is the same. I tried another set of backup, but same error....
Looking at files inside the backup (it's a zip file), i see that in xml file there is an "id"... can be this the problem?
Is it possible migrate one backup from one server, to another with higher plesk version?
thank you for your support