Abstract class and vector issue

[alexin]

I have an abstract class, SceneObject declared as follow:

#ifndef SCENE_OBJECT_H
#define SCENE_OBJECT_H

#include "Application.h"

class SceneObject{

public:
    SceneObject(void);
    virtual ~SceneObject(void);

public:
    virtual void update(Application* app)=0;
    virtual void render(Application* app)=0;
};
#endif // SCENE_OBJECT_H 

There are two more that derive from the above, an implementation...

#ifndef GROUP_H
#define GROUP_H

#include <vector>
#include "SceneObject.h"

class Group : public SceneObject{

private:
    std::vector<SceneObject> children;

public:
    Group(void);
    ~Group(void);

public:
    void update(Application* app);
    void render(Application* app);
};
#endif // GROUP_H 

... and a supposed more specialized abstract class:

#ifndef ACTOR_H
#define ACTOR_H

#include "SceneObject.h"

class Actor : SceneObject{

public:
    Actor(void);
    ~Actor(void);

public:
    virtual void update(Application* app)=0;
    virtual void render(Application* app)=0;
};
#endif // ACTOR_H 

As you can see, Group has a vector of SceneObjects that will eventually contain Groups or Actors.
On compile, the compiler yields

c:\program files\microsoft visual studio 9.0\vc\include\vector(716) : error C2259: 'SceneObject' : cannot instantiate abstract class
        due to following members:
        'void SceneObject::update(Application *)' : is abstract
        c:\documents and settings\alexandre\my documents\visual studio 2008\projects\ocaso\ocaso\sceneobject.h(13) : see declaration of 'SceneObject::update'
        'void SceneObject::render(Application *)' : is abstract
        c:\documents and settings\alexandre\my documents\visual studio 2008\projects\ocaso\ocaso\sceneobject.h(14) : see declaration of 'SceneObject::render'
        c:\documents and settings\alexandre\my documents\visual studio 2008\projects\ocaso\ocaso\group.h(10) : see reference to class template instantiation 'std::vector<_Ty>' being compiled
        with
        [
            _Ty=SceneObject
        ]

Any help is welcome.