A lot of people seem to be having problems getting Apple's X11 version to work with their international keyboards. Skimming the web, I found this to be a good way of solving it (part of it taken from some mandrake linux forum):
% xmodmap -pke .yourlanguage.xmodmap
% xmodmap .yourlanguage.xmodmap
exec xmodmap .yourlanguage.xmodmap[Editor's note: I have not tested this one...]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030113063118705