No luck with sftp, nor ftp.
Further investigation reveals that the user has apparently been removed entirely from lara. (No home directory, no entry in /etc/passwd for the account).
I’ve sent an inquiry to support@dreamhost, with specifics of the account in question and my customer information, so hopefully they can shed some light on the issue. (I don’t want to post those details to a forum).
Needless to say, it’s very disturbing that I received no advance warning, or even any notification, that a user account I created (and more importantly, the data in the user directory), was removed (or – I’m hoping – just moved elsewhere).
Thanks for your help anyway, sXi.