Need help Segmentation Fault in C++

I'm playing around with Octrees...and i've been getting "Program received signal SIGSEGV, Segmentation fault".....here are "sections" of my code and the comments showing which line the debugger stopped at and saying Segmentation fault....I was thinking it may be dealing with my "class Octree" constructor but I've no idea how to repair it....really need your help...if you still don't get the whole picture please do ask which part of the code you need....I'm using Codeblocks...I've tested on 3 different 3D models.... 1. i_pts = 2560 --> worked , 2. i_pts = 13476 --> didn't work, 3. i_pts 79938 --> didn't work

In Octree.h

class OctreePoint
{
private:
    Point position;
public:
    OctreePoint();
    OctreePoint(const Point& pos);
    ~OctreePoint();

    //....other functions
};

class Octree
{
private:
    Point origin;         // The physical center of this node
    Point halfDimension;  // Half the width/height/depth of this node
    Octree *children[8]; // Pointers to child octants
    OctreePoint *data;   // Data point to be stored at a node

public:
    Octree(const Point& _origin, const Point& _halfDimension);
    ~Octree();

    //....other functions
};

In Octree.cpp

Octree::Octree(const Point& _origin, const Point& _halfDimension)
    :origin(_origin), halfDimension(_halfDimension), data(NULL)
{
    for(int i=0; i<8; i++)
        children[i] = NULL;
}

Octree::~Octree()
{
    for(int i=0; i<8; i++)
        delete children[i];
}

int Octree::getOctantContainingPoint(const Point& point) const
{
    int oct = 0;
    if(point.x >= origin.x) oct |= 4;
    if(point.y >= origin.y) oct |= 2;
    if(point.z >= origin.z) oct |= 1;
    return oct;
}

bool Octree::isLeafNode() const{ return children[0] == NULL; }

void Octree::inserts(OctreePoint* point)
{
    if(isLeafNode()){
        if(data==NULL){
            data = point;
            return;
        }
        else{
            OctreePoint* oldPoint = data;
            data = NULL;

            for(int i=0; i<8; i++){
                Point newOrigin = origin;
                newOrigin.x += halfDimension.x * (i&4 ? .5f : -.5f);
                newOrigin.y += halfDimension.y * (i&2 ? .5f : -.5f);
                newOrigin.z += halfDimension.z * (i&1 ? .5f : -.5f);
                children[i] = new Octree(newOrigin, halfDimension*.5f);
            }

            children[getOctantContainingPoint(oldPoint->getPosition())]->inserts(oldPoint);
            children[getOctantContainingPoint(point->getPosition())]->inserts(point);
        }
    }
    else{
        int octant = getOctantContainingPoint(point->getPosition());
        children[octant]->inserts(point);   ///   <<------Segmentation fault here.
    }
}

In Main.cpp

Point* pts = (Point*) malloc(N_pts*sizeof(Point));
Octree *Oct;
OctreePoint *octPoints;

int main()
{
    //....
    Oct = new Octree(Point(0.0,58.5,-1.10,0), Point(41.0,119.0,48.0,0)); // <<---these values will be different for different 3D models....
    octPoints = new OctreePoint[i_pts];
    for(int i=0; i<i_pts; i++)
    {
        f_in >> pts[i];
        octPoints[i].setPosition(pts[i]);
        Oct->inserts(octPoints + i);   /// <<-----
    }
    //....
}