Eureka! I found the loginwindow problem. More than likely when you install software that needs to load at login, the installer will write a Login Hook in the /etc/stty file. After making a copy (cp /etc/ttys /etc/ttys.orig) I edited the line out that contained the Login Hook and uncommented the previous #console line in the file. Reboot and presto, all accounts can log in again.
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