Emptying the Recycle Bin allowed me to re-enter the user with the correct spelling, and also removed the user from the machine's "linux users".
Another question about ISPConfig users, I'd like to know if my understanding is correct.:
When I Setup the Client, I created an administrator user under ISP Manager > ISP Client > Login Data.
This "Client Admin User" did not seem to create a "real linux user", am I understanding this correctly that this is user "internal" to ISPConfig?
When I Setup the Client's Site, I created a site user under ISP Manager > ISP Site > User & Email, with the Admin box checked.
This "Site Admin User" does create a "real linux user".
The Client Admin can login to the ISPConfig control pannel on port 81, but can not connect to the site with FTP.
The Site Admin can not login to the ISPConfig control pannel, but can connect to the site with FTP.
Thanks again, Cla.