I found CCDirector::popScene may cause memory leak on some occasions.
The thing is, when u popScene more than once in a single frameupdate, like

CCDirector::sharedDirector()::popScene()
CCDirector::sharedDirector()::popScene()

then everything between current scene and last scene will be leaked out. Which could be a lot of stuffs out there.
I modified the code as below and it worked fine until now.

void CCDirector::popScene(void)
{
    CCAssert(m_pRunningScene != NULL, "running scene should not null");

    CCScene *current = (CCScene*)m_pobScenesStack->lastObject();
    if( current->isRunning() )
    {
        current->onExit();
    }
    current->cleanup();

    m_pobScenesStack->removeLastObject();
    unsigned int c = m_pobScenesStack->count();

    if (c == 0)
    {
        end();
    }
    else
    {
        m_bSendCleanupToScene = false;
        m_pNextScene = (CCScene*)m_pobScenesStack->lastObject();
    }
}