Unfortunately, the problems were not really solved. Later I checked it again and found that it sometimes doesn't work. I could eventually found the condition causing it.
If I open any application and close it, the problems happen again.
For instance, it works fine on gedit then I close all the gedit windows and open it again. Now all the problems are back. It doesn't matter what application I open and close. Even opening nautilus and closing it causes the problem. Once it's done, it happens in any applications until I log out and in again.
So if I open nautilus and close the nautilus window, the problems start happening in gedit, terminal, Pidgin, LibreOffice, etc.
I followed Alex's instructions https:/ /bugs.launchpad .net/ubuntu/ +source/ ibus-hangul/ +bug/840823/ comments/ 25 and it seemed to work fine at first (It worked after re-starting though. Logout wasn't enough).
Unfortunately, the problems were not really solved. Later I checked it again and found that it sometimes doesn't work. I could eventually found the condition causing it.
If I open any application and close it, the problems happen again.
For instance, it works fine on gedit then I close all the gedit windows and open it again. Now all the problems are back. It doesn't matter what application I open and close. Even opening nautilus and closing it causes the problem. Once it's done, it happens in any applications until I log out and in again.
So if I open nautilus and close the nautilus window, the problems start happening in gedit, terminal, Pidgin, LibreOffice, etc.
I'm seriously considering reinstalling Ubuntu 11.04.