Whether you realize or not, fcitx, a popular input method, if not properly uninstalled, can cause the notorious login loop issue on Ubuntu (i.e., every time you type your password and enter, you get asked to type your password again on the same login window). Here is the post talking about how to fully uninstall fcitx, as well as sogoupin, on Ubuntu.
http://jingyan.baidu.com/article/9faa723154c3dc473d28cb41.html
You may also encounter “fcitx-skin-sogou” problem afterwards. So here is a solution:
http://forum.ubuntu.org.cn/viewtopic.php?t=416810&p=3000862
You may then face the login loop issue, which can be solved by reinstalling ubuntu-session and ubuntu-desktop in this case.
http://askubuntu.com/questions/283985/unable-to-load-session-ubuntu-in-12-04
And then after many glitches I ended up with using IBus. Shiiiiiit.