Kubuntu 15.04 alt key problem after upgrade

Question

After last upgrade, when I do any alt+key combination my plasma window manager freezes as if the alt key keeps pressed. So I can only move windows. I have to connect with ssh to restart display manager (sddm) to get rid of it. I tried

1. With Gnome everything works like a flower
2. Removing the xorg.conf does not change anything
3. Removing the ~/.kde and restart window manager does not change anything

Does anybody have an idea? I lost the taskbar too now :-(

Answer 1

The only way I found for the moment was to move content of ~/.config file ...

1. ctrl+alt+f1
2. log in
3. sudo service sddm stop
4. mv ~/.config ~/.config_$(date +%Y%m%d_%H%M%S)
5. sudo service sddm start

and worked... for the moment dont want to search which file or directory was responsible for this behaviour...