For some time now content assist and the command panel have been broken in Eclipse and Ubiquity running under Ubuntu; they wouldn’t trigger the pop-up menues when pressing CRTL+Space.
The reason is ibus intercepting that key combination and it’s just as easily solved [1]:
- Open gconf-editor.
- Choose desktop -> ibus -> general -> hotkey.
- Open trigger parameter.
- Remove Ctrl+Space key combination from the list and press OK.
Resources
[1] Ctrl+Space doesn’t work in NetBeans [Ubuntu 12.04] [Solved]
http://jetcracker.wordpress.com/2012/05/01/ctrl-space-doesnt-work-ubuntu/
George's Techblog 
*remember to kill the ibus daemon:*
$ ps aux|grep ibus
4476 0.0 0.0 279264 3640 ? Ssl Apr19 0:24 /usr/bin/ibus-daemon –daemonize –xim
4477 0.0 0.0 134928 948 ? Sl Apr19 0:00 /usr/lib/x86_64-linux-gnu/ibus/ibus-gconf
4479 0.0 0.4 651804 19076 ? Sl Apr19 0:15 /usr/bin/python /usr/share/ibus/ui/gtk/main.py
4481 0.0 0.0 297868 2456 ? Sl Apr19 0:00 /usr/lib/x86_64-linux-gnu/ibus/ibus-x11 –kill-daemon
$ kill -TERM 4476
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I did not try it, but killing the process (i.e. killall ibus) might make the UI unresponsive. It's probably better to just log out and in again 🙂
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