Pygame - Problems With Displaying Images With Alpha

Question

I have a title screen loop, that takes the title screen and slowly fades it out. It's copied directly from another program of mine, in which it works like a charm. But it just doesn't work here. It delays correctly, but the image on the screen doesn't change. Any ideas?

titlescreen.set_alpha(255)
title_alpha_value = 255
screen.blit(titlescreen, (0, 0))
pygame.display.flip()

while not past_title:

for event in pygame.event.get():

    if event.type == pygame.QUIT:
        sys.exit('Thanks for playing!')

    elif event.type == pygame.KEYDOWN or event.type == pygame.MOUSEBUTTONDOWN:

        while titlescreen.get_alpha() >= 1:

            title_alpha_value -= 5
            screen.fill(128, 128, 128)

            titlescreen.set_alpha(title_alpha_value)
            screen.blit(titlescreen, (0, 0))
            pygame.display.flip()

            pygame.time.delay(1)

        past_title = True

        break