I recently worked through the process of creating a CRM test server from a CRM production database backup. The production database was approximately 35 GB. The database backup and restore went as expected. However, when I attempted to Import the Organization using the CRM Deployment Manager, the import would hang for several hours and then fail. The import appeared to be hanging during the Update User step.
I was able to resolve the issue following the steps in this KB Article. The import completed successfully after making the suggested changes.