Pharos Support is aware of an issue affecting some Mac systems, and is working on an appropriate solution. Any further updates will be added to this Knowledge Base article.
At this time, the problem is believed to be related to DNS resolution failing early in the boot process. To work around this, you can try adding your SignUp Server hostname to your /etc/hosts file, or altering the SignUp Client property list with the following command:
defaults write /Library/Preferences/com.pharos.signup "Server Address" $(dig -q $(defaults read /Library/Preferences/com.pharos.signup "Server Address") +short)
This command (all one line) needs to be run either before you reboot into the SignUp client the first time, or via an ssh session.
If you wish to disable the SignUp client and restore the Mac to its original login configuration, you can perform the following steps in single user mode, or via ssh if you have remote login enabled on the Mac. For ssh, you must log in as an Administrative user.
sudo cp authorization.backup authorizationEnter your password when prompted.