为什么Pygame中的精灵不会在Windows 7中出现在屏幕上？

在过去一周左右的时间里，我一直在研究太空入侵者类型的游戏，而且它的进展非常顺利，但出于某种原因我在Windows计算机上运行游戏（我喜欢编写的游戏），精灵没有出现，或只是在他们在屏幕上朝某个方向移动时出现 . 当我在我的Mac上运行完全相同的代码时，所有内容都会完美地更新 . 这是一个已知的问题，pygame只是与Windows不相处？一切都在我的Mac上工作的事实让我觉得这不是我的代码的问题，但为了以防万一，这是我的主循环：

dirty = []
score_label = font.render("Score: " + str(score), 1, (255,215,0))
level_label = font.render("Level: " + str(level), 1, (255,215,0))
screen.blit(background,(10,10),(10,10,330,30))
screen.blit(score_label,(10,10))
screen.blit(level_label,(200,10))
dirty.append((10,10,330,30))

# New level
if isEmpty(enemies):
    dirty.append((400,300,150,30))
    for i in bullets:
        dirty.append(i.pos)
        screen.blit(background,(i.pos[0],i.pos[1]),i.pos)
        bullets.remove(i)
    if pauseCounter == 40:
        screen.blit(background,(400,300),(400,300,150,30))
        pauseCounter = 0 
        jump = 30
        level+=1    
        for x in range(1,6):
            for y in range(11):
                enemies[x-1].append(Sprites.Enemy(enemy_values[6-x],(60*y,40*x),6-x))
        for x in range(len(enemies)):
            for e in enemies[x]:
                dirty.append(e.pos)
    else:
        upLevelLabel = levelFont.render("Next Level!",1,(255,215,0))
        screen.blit(upLevelLabel,(400,300))
        pauseCounter += 1

# Player input
dirty.append(o.pos)
screen.blit(background,(o.pos[0],o.pos[1]),o.pos)
keys = pygame.key.get_pressed()
if keys[K_a] and o.pos[0]-10 >= 0:
    o.speed = -10
    o.move()
if keys[K_d] and o.pos[0] <= 907-o.pos[3]-10:
    o.speed = 10
    o.move()
dirty.append(o.pos)
screen.blit(o.image,o.pos)

# Add bullets
for event in pygame.event.get():
    if event.type == pygame.QUIT: sys.exit()
    if event.type == pygame.KEYDOWN:
        if event.key == K_SPACE:
            bullets.append(Sprites.Bullet(bullet,(o.pos[0]+28,o.pos[1])))

# Updates bunkers
for b in bunkers:
    screen.blit(b.image,b.pos)
    if b.health == 0:
        screen.blit(background,(b.pos[0],b.pos[1]),b.pos)
        dirty.append(b.pos)
        bunkers.remove(b)

# Check if bullets are offscreen/collide, move accordingly
for b in bullets:
    dirty.append(b.pos)
    if b.pos[1] < 0:
        screen.blit(background,(b.pos[0],b.pos[1]),b.pos)
        dirty.append(b.pos)
        bullets.remove(b) 
    if isEmpty(enemies) == False:
        for x in range(len(enemies)):
            if len(enemies[x]) > 0:
                temp = enemies[x][0]
                if b.pos[1] in range(temp.pos[1],temp.pos[1]+temp.pos[3]):
                    for e in enemies[x]:
                        if b.pos.colliderect(e.pos):
                            score += e.val*10
                            screen.blit(background,(b.pos[0],b.pos[1]),b.pos)
                            screen.blit(background,(e.pos[0],e.pos[1]),e.pos)
                            dirty.append(e.pos)
                            dirty.append(b.pos)
                            bullets.remove(b)
                            enemies[x].remove(e)
    for i in bunkers:
        if b.pos.colliderect(i.pos):
            screen.blit(background,(b.pos[0],b.pos[1]),b.pos)
            dirty.append(b.pos)
            i.health -= 1
            bullets.remove(b)
for b in bullets:
    dirty.append(b.pos)
    screen.blit(background,(b.pos[0],b.pos[1]),b.pos)
    b.move()
    screen.blit(b.image,b.pos)
    dirty.append(b.pos)

# Moves enemy at appropriate pace, drops bombs
if enemyMoves == jump:
    moveCounter += 1
    if moveCounter == 20:
        jump = jump/2
        moveCounter = 0
    enemyMoves = 0
    for x in range(len(enemies)):
        for e in enemies[x]:
            dirty.append(e.pos)
            screen.blit(background,(e.pos[0],e.pos[1]),e.pos)
            e.move()
            screen.blit(e.image,e.pos)
            dirty.append(e.pos)
else:
    for x in range(len(enemies)):
        for e in enemies[x]:
            screen.blit(e.image,e.pos)
    enemyMoves+=1

pygame.display.update(dirty)
clock.tick(30)
print clock.get_fps()

提前致谢！