Hello Oddonelynx,
Is the image bellow what you are seeing?
If so try changing your rendering system from OpenGL to Direct3D9.
You can do this by going into the main FeralHeart folder, locating the "ogre.cfg"
open it and where it says;
Render System=OpenGL Rendering System
Replace it with
Render System=Direct3D9 Rendering System
If you are already using Direct3D9, try OpenGL
If this is not your issue could you please provide a screenshot?