Hello,

I just recently upgraded to Kubuntu 15.04. I had an initial issue with black screen before even reaching the Plymouth which was resolved by booting in revocery mode to set the proper graphics drivers (NVidia).
I now have an issue that occured without having changed any system settings : it started as me opening system settings, and getting a message telling me there were no focuses therefore nothing to show, and the app quit. I decided to reboot to see if it resolved the issue, only to be greeted with a black screen after logging in... I am now writing from failsafe mode (which also gives me black screen after log in). I do however have a somewhat working X session -- from TTY1 I was able to launch firefox -- display :1. I do also have the search bar that appears if I press alt+space, but no results show up.

My setup : I7 3770 3.4 ghz quad core, asus motherboard, NVidia GTX 560 Ti graphics. running the latest NVidia drivers. I would try to revert to something else, but I don't have access to my settings.

If anyone has any input, it would be appreciated. If you need me to paste log files, I will do my best to get them to you.

Followup : I attempted to correct the issue by upgrading to the devel version thru do-release-upgrade, it installed successfully, but still the same issue. No control panel, no DE after login, yet functional X environment because once again I can launch apps thru the TTY1 console.

Did you try reporting your issue in the Kubuntu forums?

Iève done some more digging on the forums and found an issue that seems to be narrowly related, so I will keep posting there. Thank you!!