Pygame: keys freeze up temporarilly in the middle of game

Question

I am using Python 3.4 with Pygame 1.9.2 on a windows 8 hp computer. I am working on a simple snake game where the worm eats the apple and gets longer. The code seems to be fine as far as I know, and the game works for what I have so far (worm doesn't grow yet). But the problem I'm having is that while I am testing the game it will occasionally, temporarily freeze the keys. The game will still run, but I can't use the keys for a few seconds or so, causing game over as the worm runs into the edge of the window. If I leave the curser within the screen and click, the functionality will return sooner, but you shouldn't have to deal with this problem while playing a snake game. Every second counts! Any suggestions?

    import pygame
    import time
    import random
    pygame.init()

    white = (255,255,255)
    black = (0,0,0)
    red = (255,0,0)
    green = (0,255,0)

    display_width = 800
    display_height = 600

    gameDisplay = pygame.display.set_mode((display_width,display_height))
    pygame.display.set_caption("Game Experiment")

    clock = pygame.time.Clock()

    framePsecond = 10
    block_size = 10
    font = pygame.font.SysFont(None, 25)

    def message_to_screen(msg,color):
        screen_text = font.render(msg, True, color)
        gameDisplay.blit(screen_text, [display_width/2 - 175,display_height/2])

    def gameLoop():
        gameExit = False
        gameOver = False

        lead_x = display_width/2
        lead_y = display_height/2

        lead_x_change = 0   
        lead_y_change = 0

        randApplex = round(random.randrange(0, display_width-block_size)/10.0)*10.0
        randAppley = round(random.randrange(0, display_height-block_size)/10.0)*10.0

        while not gameExit:

            while gameOver == True:
                gameDisplay.fill(black)
                message_to_screen("Game over! Press 'p' to play again or 'q' to quit",white)
                pygame.display.update()

                for event in pygame.event.get():
                    if event.type == pygame.KEYDOWN:
                        if event.key == pygame.K_q:
                            gameExit = True
                            gameOver = False
                        if event.key == pygame.K_p:
                            gameLoop()
            for event in pygame.event.get():
                if event.type == pygame.QUIT:
                    gameExit = True 
                if event.type == pygame.KEYDOWN:
                    if event.key == pygame.K_LEFT:
                        lead_x_change = -block_size
                        lead_y_change = 0
                    elif event.key == pygame.K_RIGHT:
                        lead_x_change = block_size
                        lead_y_change = 0
                    elif event.key == pygame.K_UP:
                        lead_y_change = -block_size
                        lead_x_change = 0
                    elif event.key == pygame.K_DOWN:
                        lead_y_change = block_size
                        lead_x_change = 0

            if lead_x >= display_width or lead_x <= 0 or lead_y >= display_height or lead_y < 0:
                gameOver = True

            lead_x += lead_x_change
            lead_y += lead_y_change

            gameDisplay.fill(green)
            pygame.draw.rect(gameDisplay, red, [randApplex,randAppley,block_size,block_size])
            pygame.draw.rect(gameDisplay, red, [lead_x,lead_y,block_size,block_size])
            pygame.display.update()

             if lead_x == randApplex and lead_y == randAppley:
                randApplex = round(random.randrange(0, display_width-block_size)/10.0)*10.0
                randAppley = round(random.randrange(0, display_height-block_size)/10.0)*10.0

            clock.tick(framePsecond)

        pygame.quit()
        quit()


    gameLoop()