1) try to change ur Windows Language in English (USA)
if the game doesn't work now, use 2)
2) change ur Windows Language in English ( USA). "If you have 1 or more folders ( if u install it more as 1 times) , uninstall the programm (and delete the COMPLETE folder!). Reinstall, when you get the step that asks for a directory, CHANGE THE DIRECTORY NAME SO THERE IS NOT A SPACE AT THE END OF THE NAME. Now install it. DO NOT launch the game, download http://files.zefie.net/public/ROSE/ROSEonline.rar or here http://mitglied.lycos.de/nur4dich/ROSEonline.rar , and install it to your rose online folder and make sure it OVERWRITES . then open the client and patch."
3) If this both versions doesn't work .. just update ur Windows with the Service Pack 2 (XP) and try 1) and 2)