I was updating an iPhone 4G to iOS7on Ubuntu 13.10 through virtualbox and iTunes running on Windows XP. You have to pay attention during this process and re-attach the USB device whenever the process restarts the iPhone. Alternatively you may create a rule to attach the iPhone automatically.
After updating, during sync, the iPhone couldn’t finish restoring user’s data. Ubuntu was trying to mount the device even when the rule was in place on virtualbox to attach the iPhone automatically. It seems that they both compete to mount the device, causing the sync to be dropped. Finally I noticed that Ubuntu was creating a ‘Documents on iPhone’ mount point, I unmounted this from nautilus and restarted the sync on virtualbox and it all went well at last.