Site in Maintenance Mode, Admin logged in, Member has a 4 character name and a password that is the same as the member name.
Related bug report on member name/password being the same:
http://www.elkarte.net/community/index.php?topic=1639.0 (http://www.elkarte.net/community/index.php?topic=1639.0)
When Admin attemts to change the member password via the member Profile this error is produced.
Fixed here:
https://github.com/emanuele45/Dialogo/commit/94b05c7c92ceaff56d2afa3e2541efd876285fea