Trying to install ubuntu-desktop was (according to synaptic) not possible because ubuntu-sounds could not get installed. Installing ubuntu-sounds however was possible (4 ubuntustudio- packages got removed including ubuntustudio-sounds). Afterwards ubuntu-desktop could be installed.
So it seems that
1) the update-manager tries to install ubuntu-desktop and fails at that,
2) it should not install ubuntu-desktop but upgrade ubuntustudio-desktop.
Maybe interesting:
Trying to install ubuntu-desktop was (according to synaptic) not possible because ubuntu-sounds could not get installed. Installing ubuntu-sounds however was possible (4 ubuntustudio- packages got removed including ubuntustudio- sounds) . Afterwards ubuntu-desktop could be installed.
So it seems that desktop.
1) the update-manager tries to install ubuntu-desktop and fails at that,
2) it should not install ubuntu-desktop but upgrade ubuntustudio-