Append your source list
$ sudo vi /etc/apt/sources.list
deb http://ftp.kr.debian.org/debian/ unstable main
$ sudo apt-get update
$ sudo apt-get install nabi
Then, remove deb [WWW] http://ftp.kr.debian.org/debian/ unstable main in your source list and apt-get update again to refresh source list
$ cd
$ vi .gnomerc
export XMODIFIERS="@im=nabi"
export GTK_IM_MODULE=xim