I've found out that reverting the package "compiz-plugins-main-default" version 0.9.6-0ubuntu4 to version 0.9.6-0ubuntu2 solves this problem, as well as the incorrect Ctrl-Alt-KP_9 behaviour.
I've found out that reverting the package "compiz- plugins- main-default" version 0.9.6-0ubuntu4 to version 0.9.6-0ubuntu2 solves this problem, as well as the incorrect Ctrl-Alt-KP_9 behaviour.