Bug#655328: gdm3: No, your mistake.

[Sergio Cipolla]

:) sorry if I sounded harsh, I hadn't read the other replies.
Interesting that you don't have greeter.gconf.defaults (it must have been
deleted some time as it still comes in the package - but I think Debian has
this thing of not reinstating the config file even when we purge the
package and reinstall it again), I had a problem trying to change the
cursor theme and only succeeded after editing greeter.gconf.defaults