error: invalid use of incomplete type 'struct Foo'

[ShotoReaper]

Llevo analizando este error un rato y no veo donde falla. Estos son los errores que me da:

Código:

C:\Users\Héctor\Documents\Visual Studio 2010\Projects\GekkoEngine\src\Components\../../include/Cube.hpp:12: error: invalid use of incomplete type 'struct Component'
C:\Users\Héctor\Documents\Visual Studio 2010\Projects\GekkoEngine\src\Components\../../include/GameScreen.hpp:14: error: forward declaration of 'struct Component'

GameScreen

Código:

#ifndef GAMESCREEN_H
#define GAMESCREEN_H

#include <string>
#include <list>
#include <iostream>
#include <functional>
#include <algorithm>
#include "Util.hpp"
#include "object.hpp"
#include "Component.hpp"

class Engine;
class Component;    // Line 14

class GameScreen : public object
{

    public:
        GameScreen(std::string);

        void setEngine(Engine *engine);
        Engine* getEngine(void);

        void setName(std::string);
        string getName(void);

        void AddComponent(Component*);
        void RemoveComponent(Component*);
        void PutComponentInOrder(Component*);

        void LoadGameScreen(void);

        virtual void Draw(void);
        virtual void Update(void);

        // Sobrescribimos el operador == para poder hacer nuestra propia comparacion
        // friend: no pertenece a la clase, pero puede usar sus miembros
        friend bool operator == (const GameScreen &gs1, const GameScreen &gs2);
        GameScreen& operator = (const GameScreen &gs);

    protected:
        virtual void Load(void);

    private:

        string name;

        static Engine* engine;

        std::list<Component*> components;

        bool loaded;


};

struct CompareGS : public std::binary_function < GameScreen*, GameScreen*, bool>
        {
            bool operator() (const GameScreen* gs1, const GameScreen* value) const
            {
                return (gs1 == value);
            }
        };

#endif // GAMESCREEN_H

Cube

Código:

#ifndef CUBE_H
#define CUBE_H

#include "../glm/gtc/matrix_transform.hpp"
#include "../glm/gtc/type_ptr.hpp"
#include "../include/GraphicsUtil.hpp"
#include "Component.hpp"
#include "GameScreen.hpp"

class Cube : public Component
{                                                       // Line 12
    public:
        Cube();
        void Update(void);
        void Draw(void);
    protected:
        void Initialize(void);
        void Load(void);
    private:
        static Mesh* mesh;

        static Shader* shader;

        static GLuint
                        ShaderIds[3],
                        TextureId;

        static  GLuint  ModelMatrixUniformLocation,
                        Tex0Loc;

        static mat4 	ModelMatrix;
};

#endif // CUBE_H