I experienced a lot of trouble making my skype installation on ubuntu 7.04 feisty fawn accepting korean input as there is a incompatibility of the scim IME and the skype client (or the qt-lib used as some mention). However these problems got solved when I installed the nabi IME, which is more convenient anyway. I hope this information helps others who have the same problem. Further information on nabi and korean input editors:
http://www.ubuntu.or.kr/wiki.php/InstallingInputMethods (korean)