Não me lembro como consertei isso, mas hoje em dia, basta atualizar para o 16.04 ou superior e ele funcionará bem novamente.
Eu fiz o upgrade para 15.10 e agora o Notes não inicia (provavelmente porque eles mudaram a barra de rolagem).
Gtk-Message: Failed to load module "overlay-scrollbar"
Gtk-Message: Failed to load module "unity-gtk-module"
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
(notes:12215): Gtk-WARNING **: Unable to locate theme engine in module_path: "murrine",
Existe alguma solução para isso?
Não me lembro como consertei isso, mas hoje em dia, basta atualizar para o 16.04 ou superior e ele funcionará bem novamente.