I do have some suggestions as I too have had many network/credentials related errors with these Windows builds. Try some of these suggestions if you haven't already:
1. Disable Windows Firewall.
2. Disable Windows Defender.
3. Enable the administrator account as it is disabled by default in Windows Vista and 7.
4. Enable Remote Desktop.
5. Make sure the Remote Registry service is running.
6. Check the settings of how Windows Vista and 7 share files. Some of these settings can mess with things.
7. If providing credentials, make sure the user you select doesn't have a blank password
8. Try local user account credentials rather than domain-based.
8. Run a gpupdate /force to ensure those boxes have all the latest policies.
9. Set Anitivirus as disabled during deployment.
10. Use classic Domain\Username rather than
user@domain.com
Hopefully, one of these will help...........