c++ SDL runtime errors

#include <iostream>
#include <SDL.h>
#include <SDL_ttf.h>
#include <SDL_Image.h>
#include "paddle.h"
#define FPS 30

using namespace std;

SDL_Surface * screen;
SDL_Event event;
Uint32 start;

bool keys[256];
bool fullscreen = false;
bool running = true;

bool init();

int main(int argc,char** argv)
{
	if((!init())){SDL_Quit(); return 0;}
	paddle paddle1(1);
	paddle paddle2(2);

	while(running)
	{
		start = SDL_GetTicks();
		while(SDL_PollEvent(&event))
		{
			switch(event.type)
			{
			case SDL_QUIT:
				running = false;
				break;
			case SDL_KEYUP:
				keys[event.key.keysym.sym] = false;
				break;
			case SDL_KEYDOWN:
				if(event.key.keysym.sym == SDLK_f){fullscreen = (!fullscreen);}
				if(event.key.keysym.sym == SDLK_ESCAPE){running = false; break;}
				keys[event.key.keysym.sym] = true;
				break;
			}
		}
		if(keys[SDLK_w]){cout << "W IS DOWN" << endl; paddle1.Up();}
		else if(keys[SDLK_s]){cout << "S IS DOWN" << endl; paddle1.Down();}
		if(keys[SDLK_UP]){cout << "ARROWUP IS DOWN" << endl;paddle2.Up();}
		else if(keys[SDLK_DOWN]){cout << "ARROWDOWN IS DOWN" << endl; paddle2.Down();}

		if(fullscreen){screen = SDL_SetVideoMode(800,600,32,SDL_HWSURFACE|SDL_DOUBLEBUF|SDL_FULLSCREEN);}else{screen = SDL_SetVideoMode(800,600,32,SDL_HWSURFACE|SDL_DOUBLEBUF);}

		SDL_FillRect(screen,NULL,NULL);

		paddle1.Blit();
		paddle2.Blit();

		SDL_Flip(screen);
		if(1000/FPS > SDL_GetTicks() - start){SDL_Delay(1000/FPS - (SDL_GetTicks() - start));}
	}
	SDL_Quit();

	return 0;
}

bool init(){

	if(SDL_Init(SDL_INIT_EVERYTHING) == -1){
		std::cout << "Could not initialize sdl" << std::endl;
		return false;
	}
	std::cout << "SDL initilized" << std::endl;

	screen = SDL_SetVideoMode(800,600,32,SDL_HWSURFACE|SDL_DOUBLEBUF);

	if(screen == NULL){
		std::cout << "Could not setup screen" << std::endl;
		return false;
	}

	std::cout << "Screen is setup" << std::endl;


	if(TTF_Init() == -1){
		std::cout << "Could not initialize ttf" << std::endl;
		return false;
	}

	std::cout << "TTF initilized" << std::endl;

	SDL_WM_SetCaption("Pong",NULL);

	return true;

}

#pragma once
#include <iostream>
#include <SDL.h>
#include <SDL_ttf.h>
#include <SDL_Image.h>

#include "global_functions.h"


class paddle
{
public:
	paddle(short nr);
	~paddle(void);

	void Up();
	void Down();
	void Blit();

	
private:
	int YVel;
	SDL_Surface * image;
	SDL_Rect box;
};

#include "paddle.h"


paddle::paddle(short nr)
{
	global_functions f;
	image = f.Load_Image("paddle.jpg");
	image->refcount++;
	YVel = 5;
	box.w = image->w;
	box.h = image->h;
	box.y = SDL_GetVideoSurface()->h/2 - box.h/2;
	switch(nr)
	{
	case 1:
		box.x = 0;
		break;
	case 2:
		box.x = SDL_GetVideoSurface()->w - box.w;
		break;
	}

}

void paddle::Up()
{
	box.y-=YVel;
}

void paddle::Down()
{
	box.y+=YVel;
}

void paddle::Blit()
{
	SDL_BlitSurface(image,NULL,SDL_GetVideoSurface(),&box);
}

paddle::~paddle(void)
{
	SDL_FreeSurface(image);
}

SDL_Surface * global_functions::Load_Image(std::string filename){

	image = IMG_Load(filename.c_str());

	if(image != NULL){
	Optimized_Image = SDL_DisplayFormat(image);
	}
	else{
		std::cout << "Image could not be loaded" << std::endl;
	}
	return Optimized_Image;
}