Note: this is about OS X Tiger with an ancient X11 based of XFree86:
Apples 'X11 v. 1.1.3 - XFree86 4.4.0'
which has limited support for clipboard syncing between osx native applications and software running under X11 as well as a different default X11 keymapping (than current X.org based X11/Xquartz versions shipped with Leopard and Snow Leopard) for 'Option/Alt' ('option'+o' would require the option key to be mapped to 'Mode_switch', but afaik that X11 version maps both option keys to Alt_L resp. Alt_R), which is good because Inkscape shortcuts work out of the box (no need for custom ~/.Xmodmap settings), otoh one looses the ability to enter diacritics or other special characters via keyboard entry.
Is there a setting in your X11 preferences to 'Follow system keyboard layout'?
Yes, I have it - and it ist choosen.
Greetings,
Wolf