bool TetrisBlockBase::OnRender(float timeSinceLastFrame)
{
    bool destroyMe = false;

    if (this->moving) //segfault here
    {
...

class TetrisBlockBase
{
    public:
        //constructor: mx and my are in game grid coordates: 0,0 being the bottom left corner and 9,19 being the top right corner. mNode is an already initialized scene node
        TetrisBlockBase(Ogre::SceneNode* node, int mx, int my);
        virtual ~TetrisBlockBase();

        TetrisKnockResult Knock(TetrisKnockCondition* condition); //This is called when this block needs to be knocked

        bool DescendTo(int y); //this is called to make the block descend to a new position. Returns false if it is unable to move because the requested y is too high.
        bool AtRequestedLocation(); //returns true if the scene node's position matches the game grid coordinates requested (i.e. is the movement animation finished?)
        bool OnRender(float timeSinceLastFrame); //if this returns false, this object should be destroyed. This is called just before the frame is to be rendered
    protected:
        Ogre::SceneNode* mNode;

        int gx, gy; //the game grid coordinates of this block

        int request; //requested game grid y coordinate

        bool knocked; //whether or not this block is knocked
        bool moving; //whether or not this block is moving down
        Ogre::Vector3 acceleration; //acceleration of this node if it is knocked or moving
        Ogre::Vector3 velocity; //velocity of this node if it is knocked or moving
};