While looking to my logs I saw this error message:
(gsettings-data-convert:14691): GLib-GIO-ERROR **: Settings schema 'org.gnome.devhelp.state.assistant.window' does not contain a key named 'maximized' and gsettings-data-convert crashes right away.

/usr/share/GConf/gsettings/devhelp.convert reports a key
[org.gnome.devhelp.state.assistant.window]
maximized=/apps/devhelp/state/assistant/window/maximized
and the key exists in the gconf schema. 

I guess the problem comes from /usr/share/glib-2.0/schemas/org.gnome.devhelp.gschema.xml which doesn't have a maximized key for the schema id "org.gnome.devhelp.state.assistant.window".

I don't know lot about gsetting and I hope my assumptions are right. I can cook a patch if you want.

Perhaps another bug should be open against gsettings-data-convert to make it more robust against missing key.