Mouse control not responding

I've just started using pygame. I've created my game but it's really unstable and crashes (having issues exiting).

I've created a welcome page but it has created a bug with game control (the character controlled by the mouse has stopped responding), I've tried few methods but just results in more game crashes and errors. can you please help me out to debug anything you might spot. you download the game from her http://dl.dropbox.com/u/47312995/Twerk.rar

the code:

import pygame
 from pygame import *
 import random
 import time
 import os
 import sys
 from pygame.locals import *
 
 
 black = (0,0,0)
 white = (255,255,255)
 
 pygame.init()
 
 def game():
 
 os.environ['SDL_VIDEO_CENTERED'] = '1'
 mouse.set_visible(False)
 screen = display.set_mode((800,500))
 backdrop = pygame.image.load('bg.jpg').convert_alpha()
 menu = pygame.image.load('green.jpg').convert_alpha()
 ballpic = pygame.image.load('ball.gif').convert_alpha()
 mouseball = pygame.image.load('mouseball.gif').convert_alpha()
 display.set_caption('Twerk')
 back = pygame.Surface(screen.get_size())
 
 def text(text,x_pos,color,font2=28):
     tfont = pygame.font.Font(None, font2)
 
     text=tfont.render(text, True, color)
     textpos = text.get_rect(centerx=back.get_width()/2)
     textpos.top = x_pos
     screen.blit(text, textpos)
 
  start = False
  repeat = False
 while start == False:
     for event in pygame.event.get():
         if event.type == pygame.QUIT:
             start = True
             #falling = True
             #finish = True
 
         if event.type == pygame.KEYDOWN:
             if event.key == pygame.K_SPACE:
                 start = True
     #game over screen
     screen.blit(menu,[0,0])
     pygame.display.set_caption("TWERK")
 
     #Text
     #"Welcome to Escape"
     #needs replacing with logo 
     text("Twerk",60,white,300)
 
     #"Instructions"
     text("Instructions",310,white)
     text("----------------------------------------------------------------------------------------",320,white)
     text("Avoid the the enemies",340,white)
     text("Last as long as you can!",360,white)
     text("Press space to start",420,white)
     pygame.display.flip()
 
 
 while start == True:
 positionx=[]
 positiony=[]
 positionxmove=[]
 positionymove=[]
 falling = False
 finish = False
 score=0
 enemies=1
 velocity=1
 
 for i in range(enemies):
   positionx.append(random.randint(300,400)+random.randint(-300,200))
   positiony.append(random.randint(200,340)+random.randint(-200,100))
   positionxmove.append(random.randint(1,velocity))
   positionymove.append(random.randint(1,velocity))
 
 
 font = pygame.font.Font(None, 28)
 text = font.render('Starting Twerk... ', True, (100,100,100))
 textRect = text.get_rect()
 textRect.centerx = screen.get_rect().centerx
 textRect.centery = screen.get_rect().centery
 
 screen.blit(backdrop, (0,0))
 screen.blit(text, textRect)
 pygame.display.update()
 game=time.localtime()
 
 while start == True:
   end=time.localtime()
   score= (end[1]-game[1])*3600 + (end[4]-game[4])*60 + end[5]-game[5]
   if score > 1: break
 
 first=True
 strtTime=time.localtime()
 
 while not finish or falling:
   screen.blit(backdrop, (0,0))
   for i in range(enemies):
     screen.blit(ballpic,(positionx[i],positiony[i]))
     (mousex,mousey)=mouse.get_pos()
     screen.blit(mouseball,(mousex,mousey))
     display.update()
     strt = time.localtime()
 
   if first:
     while True:
       end=time.localtime()
       score= (end[3]-strt[3])*3600 + (end[4]-strt[4])*60 + end[5]-strt[5]
       if score > 3: break
     first = False
 
   if falling:
     for i in range(enemies):
       positionymove[i]=1000
       positionxmove[i]=0
 
 
   for i in range(enemies): positionx[i]=positionx[i]+positionxmove[i]
   for i in range(enemies): positiony[i]=min(600,positiony[i]+positionymove[i])
 
   if falling:
     falling=False
     for posy in positiony:
       if posy<600: falling=True
 
 
   if not falling:
     for i in range(enemies):
       for j in range(i+1,enemies):
         if abs(positionx[i]-positionx[j])<20 and abs(positiony[i]-positiony[j])<20:
           temp=positionxmove[i]
           positionxmove[i]=positionxmove[j]
           positionxmove[j]=temp
           temp=positionymove[i]
           positionymove[i]=positionymove[j]
           positionymove[j]=temp
 
     for i in range(enemies):  
       if positionx[i]>600: positionxmove[i]*=-1
       if positionx[i]<0: positionxmove[i]*=-1
       if positiony[i]>440: positionymove[i]*=-1
       if positiony[i]<0: positionymove[i]*=-1
 
     for i in range(enemies):
       if abs(positionx[i]-mousex)<40 and abs(positiony[i]-mousey)<40:
 
         endTime=time.localtime()
         score= (endTime[3]-strtTime[3])*3600 + (endTime[4]-strtTime[4])*60 + endTime[5]-strtTime[5]
         falling = True
         finish = True
 game()
 

Thank you in advance

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