Questions about: ibus

Seems like the correct issue/bug for OP is actually this: IDEA-78860 This is not a Ubuntu version specific, but X Window / IBus problem and it is still happening in Ubuntu 14. 04 with IBus < 1. 5
It sounds like you have Ibus running, which uses Ctrl + Space by default to enable/disable the input editor. You can change the shortcut key assigned to it in Ibus Preferences. If Ibus is running in the menubar, you can right-click to choose Preferen