Thanks for your help but I just solved it another way.
I changed the 'Language for non-Unicode programs' option (in XP) from 'Korean' to 'English' and it worked.
One guy in a Korean forum told me that some language-specific characters (such as umlaut in German) are
not supported correctly when this option is set to certain languages including Korean (even when using English
version of Windows, like me), and this causes many problems with games and other apps.
In this case there might be such characters in aircraft files. (maybe French? I'm not sure).
Thanks again for all of your help guys. Now I'm flying with this beauty.