Lightdm problem

Synaptic doesn’t run.lightdm automatically uninstalled and i could not install it it shows
linubaba@linubaba-G41M-Combo:~$ sudo apt-get install lightdm
[sudo] password for linubaba:
Reading package lists… Done
Building dependency tree
Reading state information… Done
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:
lightdm : Depends: plymouth (>= 0.8.8-0ubuntu6.1) but 0.8.8-0ubuntu6 is to be installed
E: Unable to correct problems, you have held broken packages.

This is another ppa issue I guess that has to do with the gnome ppas you activated. They seem to be incompatible even with ubuntu.