tkFileDialog closes main application

[mdmdmd]

Hello,

I wish to collect 4 files from a user.  So I have decided to use 
tkFileDialog askopenfilename.  My problem is that after a few file 
selections the root window is destroyed (the whole program just dissappears)

I have created a simple example and was able to reproduce the same thing 
with this.  I've just started using tkinter so I have no idea what I may 
be doing wrong.  If anyone has any ideas please let me know.

If you run the following code, just click the Browse button, and select 
a file.  Do this repeatedly and for me after the sixth or seventh time 
the window shuts down.

BTW, I'm using python 2.4 on Windows XP.  Thank you for any help.

################################################################################

from Tkinter import *
import Pmw
import tkFileDialog
import os.path

filepath = 'C:\\Documents and Settings\\admin\\Desktop\\'

class App(Frame):
     def __init__(self,master):
         Frame.__init__(self, master, bg='gray')
         self.enttxt = StringVar()

         lbl = Label(self,text='File 1:')
         lbl.grid(row = 0,column = 0,sticky = W,padx = 5,pady = 5)

         self.e1 = Entry(self,textvariable = self.enttxt,width = 50)
         self.e1.grid(row = 0,column = 1,columnspan = 3,sticky = W,padx 
= 5,pady = 5)

         btn = Button(self,text='Browse ...',width = 12,
                      command = self.browse)
         btn.grid(row = 0,column = 4,sticky=W,padx=5,pady=5)

     def browse(self):
         fileformats = [('Text File ','*.csv'),
                        ('All Files ','*.*')]

         retval = tkFileDialog.askopenfilename(title='Choose File',
                                               initialdir=filepath,
                                               filetypes=fileformats,
                                               parent = self)
         if retval:
             self.enttxt.set(os.path.abspath(retval))

def main():
     root = Tk()
     root.withdraw()
     root.title('test')
     root.configure(bg='gray')
     app = App(root)
     app.pack()
     root.update()
     root.deiconify()

     root.mainloop()


if __name__ == '__main__':
     main()