Looks like we've seen this before - bug 18570. It's also been reported as debian bug 385170 (see the diff attached to message #16 in that bug report).
In 18570, Martin Pitt comments, "I have the impression that gnome-system-tools' users-admin has something to do with it"
@Steve/Kees - when you did your testing, did you try adding a new user before performing the upgrade? Though I can't imagine why that would require changing whitespace in login.defs, it's the best I can come up with right now.
Looks like we've seen this before - bug 18570. It's also been reported as debian bug 385170 (see the diff attached to message #16 in that bug report).
In 18570, Martin Pitt comments, "I have the impression that gnome-system-tools' users-admin has something to do with it"
@Steve/Kees - when you did your testing, did you try adding a new user before performing the upgrade? Though I can't imagine why that would require changing whitespace in login.defs, it's the best I can come up with right now.