Ошибка установки Ubuntu-Desktop на 14.04

Я пытаюсь установить Ubuntu-Desktop на 14.04, но когда я запускаю apt-get install ubuntu-desktop это дает ошибку:

Some packages could not be installed. This may mean that you have 
requested an impossible situation or if you are using the unstable 
distribution that some required packages have not yet been created 
or been moved out of Incoming. 
The following information may help to resolve the situation:

The following packages have unmet dependencies: 
ubuntu-desktop : Depends: ubuntu-session but it is not going to be installed 
E: Unable to correct problems, you have held broken packages."

С synaptic, это показывает красную метку на этом пакете. Я пробовал с apt-get clean так же как apt-get update но безуспешно