컴퓨터상 세세한 이미지 처리는 완벽하지 않은 경우가 많습니다. 하드웨어 문제거나 소프트웨어 문제 일수 있는데, 

개발하는 도중에는 세밀한 부분에 너무 신경을 쓰지 않고 전체적으로 완성시킨후 조금씩 수정하는 편이 좋은 것 같습니다. 

A5칩 수정 http://www.cocos2d-x.org/news/24 다른 수정안도 있었는데 까먹어서-_-;

Regarding to cocos2d-iphone's post "cocos2d and iPad 2" http://www.cocos2d-iphone.org/archives/1430, cocos2d-x games have the same problem. RicardoQuesada believed it's a iPad2 bug, no cocos2d.

As the default setting, cocos2d-x uses 3D projection with a depth buffer, in CCDirector::setGLDefaultValues()

voidCCDirector::setGLDefaultValues(void)
{

     // This method SHOULD be called only after openGLView_ was initialized
     assert(m_pobOpenGLView);

     setAlphaBlending(true);
     setDepthTest(true);
     setProjection(m_eProjection);  
     // m_eProjection is set to kCCDirectorProjectionDefault in CCDirector::init(), while
     // kCCDirectorProjectionDefault is set to kCCDirectorProjection3D in CCDirector.h

     // ...

}

So for ipad2 games, don't forget to invoke

// alternative A: Disable Depth Test
CCDirector::sharedDirector()->setDepthTest(false);

OR

// alternative B: use 2D projection
CCDirector::sharedDirector()->setProjection(kCCDirectorProjection2D);

Either one is OK. After this modification, please re-test your whole game. setDepthTest may affect some effects, transitions, and tilemap z order behaviours