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- Check to make sure the ethernet connection is providing an IP address.
- Click on the Apple menu and select "Log Out".
- At the login screen, see if the 'network accounts unavailable' message goes away. If so, login with the new password.
Additional Notes
The reason they need to login to their MWS Mac with the old password initially, is because the encrypted disk still has the old password. Once the disk unlocks and the boot continues, it finds that the old password no longer works with Active Directory, and prompts for the second login. When the new password is entered and accepted, the disk password is changed to match the new password.