low framerate problem

Hi, I have a problem with my game.
After playing for several minutes framerate goes to low.

I’ve tried playing in a simple scene: 3d model draw with VBO, no collisions, simple level e no other objects and I have the same problem.
Some suggests?

Maybe something wrong with my “main” file?

main.cpp:

void display();
void animate();
void reshape(int width, int height);
void mouseFunc(int,int,int,int);
void keyboardFunc(unsigned char, int, int);
void specialKeyboardFunc(int, int, int);
void changeScene();

GameScene *game;
StartMenu *start;
SelectionScene *selection;

extern State CURRENTSTATE;

int main (int argc, char ** argv)
{
myWindow window1;
window1.init(argc, argv);

StartMenu s;
SelectionScene sl;
GameScene g;
Debug d;

start = &s;
selection = &sl;
game = &g;

glutReshapeFunc(reshape);

window1.render(&display);
window1.mouse(&mouseFunc);
window1.keyboard(&keyboardFunc);
window1.specialKeyboard(&specialKeyboardFunc);
game->setTime(glutGet(GLUT_ELAPSED_TIME));
glutIdleFunc(&animate);

glutMainLoop();

return 0;

}

void display()
{

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glDisable(GL_CULL_FACE);

glLoadIdentity();

switch (CURRENTSTATE) {
    case STARTMENU:
        if(start->initialize()) {
            start->render();
        }
        break;
    case SELECTION:
        if(selection->initialize()) {
            selection->render();
        }
        break;
    case GAME:
        if(game->initialize()) {
            game->render();
        }
        break;
    default:
        exit(1);
}

glutSwapBuffers();

}

void reshape(int width, int height)
{
switch (CURRENTSTATE) {
case STARTMENU:
start->reshape(width, height);
break;

    case SELECTION:
    {
        SelectionScene selection;
        selection.reshape(width, height);
        break;
    }
    case GAME:
        game->reshape(width, height);
        break;
    case DEB:
       // debug->reshape(width, height);
        break;
    default:
        exit(1);
}

}

void animate()
{
switch (CURRENTSTATE) {
case SELECTION:
{
selection->animate();
break;
}
case GAME:
game->animate();
break;
case DEB:
// debug->animate();
break;
default:
break;
}

}

void mouseFunc(int btn, int state, int x, int y)
{
switch (CURRENTSTATE) {
case STARTMENU:
start->mouse(btn, state, x, y);
break;

    case SELECTION:
        selection->mouse(btn, state, x, y);
        break;
        
    case GAME:
        game->mouse(btn, state, x, y);
        break;
        
    default:
        break;
}

}

void keyboardFunc(unsigned char key, int x, int y)
{
switch (CURRENTSTATE) {

    case GAME:
        game->keyboard(key, x, y);
        break;
        
    default:
        break;
}

}

Usually, people who have this problem, I point them to the Common Mistakes page.
http://www.opengl.org/wiki/Common_Mistakes#glGenTextures_in_render_function

PS: there is no point in showing us you are calling selection->animate() start->render() and such functions.