I am facing some issues with kubuntu upgrade recently using kubuntu-devel-release-upgrade from my 14.04 version, though installation finished without any error messages; after machine restart it is just a blank screen. I can see kubuntu in the screen centre while booting and will end up in a blank screen. If I press ctrl+alt+f1 it will allow me to login console and I tried few tips like reinstalling plasma-desktop etc but all in vain. I dont think this is an issue with my display drivers, since same version I tried on another partition and is working fine.
Kindly update if anyone come across similar situation.