nvoglv32.dll Access violation reading location 0x00000000 - c++

Question

I've been having a problem lately with openGL. In my program that has worked fine before, I try to draw a group of polygons to the screen but the program throws an error and for the life of me I can't find the cause of it. I've literally changed nothing from my code, it just started throwing errors one day after coming back to it after a month. The error is:
Unhandled exception at 0x69F2883E (nvoglv32.dll) in openGLtest.exe:
0xC0000005: Access violation reading location 0x00000000.
I have reproduced the error with the code below. Some more strange behavior I've noticed is that if I change the call to glDrawArrays to something like:
glDrawArrays(GL_TRIANGLES, 3, numV);
or
glDrawArrays(GL_TRIANGLES, 0, 258);
then the program doesn't throw the error though obviously it doesn't render properly, rendering only half of the rectangle, or rendering the rectangle plus some garbage input.
It's very strange, if it renders more than 255 points it works fine but any less and it throws the error.
#include <SDL.h>
#include <GL/glew.h>
#include <math.h>
#include <vector>
struct Vector2f{
public:
float x, y;
Vector2f() {}
Vector2f(float _x, float _y) { x = _x; y = _y; }
};
struct Vector3f {
public:
float x, y, z;
Vector3f() { x = 0.0, y = 0.0, z = 0.0; }
Vector3f(float _x, float _y, float _z) { x = _x; y = _y; z = _z; }
};
struct Vertex {
Vector3f m_pos;
Vector2f m_tex;
Vector3f m_normal;
Vertex() {}
Vertex(Vector3f pos, Vector2f tex) {
m_pos = pos;
m_tex = tex;
m_normal = Vector3f(0.0f, 0.0f, 0.0f);
}
Vertex(Vector3f pos, Vector2f tex, Vector3f norm) {
m_pos = pos;
m_tex = tex;
m_normal = norm;
}
};
SDL_Window* Window_Display = NULL;
SDL_GLContext glcontext;
GLuint VBO;
int width = 800;
int height = 600;
float ratio = (float)width / (float)height;
int numV;
std::vector<Vertex> _VBO;
bool initWindow() {
//draw a square
_VBO.push_back(Vertex(Vector3f(-0.8f, -0.8f, 0.0f), Vector2f(0.0f, 0.0f), Vector3f(0.0f, 0.0f, 0.0f)));
_VBO.push_back(Vertex(Vector3f(0.8f, -0.8f, 0.0f), Vector2f(0.0f, 0.0f), Vector3f(0.0f, 0.0f, 0.0f)));
_VBO.push_back(Vertex(Vector3f(0.8f, 0.8f, 0.0f), Vector2f(0.0f, 0.0f), Vector3f(0.0f, 0.0f, 0.0f)));
_VBO.push_back(Vertex(Vector3f(-0.8f, -0.8f, 0.0f), Vector2f(0.0f, 0.0f), Vector3f(0.0f, 0.0f, 0.0f)));
_VBO.push_back(Vertex(Vector3f(-0.8f, 0.8f, 0.0f), Vector2f(0.0f, 0.0f), Vector3f(0.0f, 0.0f, 0.0f)));
_VBO.push_back(Vertex(Vector3f(0.8f, 0.8f, 0.0f), Vector2f(0.0f, 0.0f), Vector3f(0.0f, 0.0f, 0.0f)));
numV = 6;
if (SDL_Init(SDL_INIT_VIDEO) < 0) return false;
if ((Window_Display = SDL_CreateWindow("OpenGL Drawing Test", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, width, height, SDL_WINDOW_OPENGL)) == NULL) return false;
glcontext = SDL_GL_CreateContext(Window_Display);
glewInit();
return true;
}
bool drawScene() {
glEnableClientState(GL_VERTEX_ARRAY);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW); //Switch to the drawing perspective
glLoadIdentity(); //Reset the drawing perspective
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glEnableVertexAttribArray(2);
glGenBuffers(1, &VBO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, numV * sizeof(Vertex), &_VBO[0], GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*)12);
glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*)20);
glDrawArrays(GL_TRIANGLES, 0, numV); //Unhandled exception at 0x69F2883E (nvoglv32.dll) in openGLtest.exe: 0xC0000005: Access violation reading location 0x00000000.
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glDisableVertexAttribArray(2);
SDL_GL_SwapWindow(Window_Display); //Send the 3D scene to the screen
glDisableClientState(GL_VERTEX_ARRAY);
return true;
}
int main(int argc, char* args[]) {
if (initWindow()) {
while (drawScene()) {}
}
return 0;
}