I seem to be locked out of my machine suddenly.  Although I can still
boot single user, any attempt to login via the console or over the
network causes 'login incorect' immediately after entering username.

Nothing in the configuration has changed.. this just started happening
when I rebooted.

I can rexec a shell, but I can't su.

I tried vipw in single user mode (with my filesystems read/write) to
rebuild the security database, but this didn't fix it.

HELP?!  Thanks.