matplotlib pylab plot() BadWindow error

[oyinbo55]

I am trying to use the pylab plot command on my laptop running Ubuntu
6.06 (Dapper).  Although the plot command works fine on my XP desktop
at work, I cannot open the plot window on the laptop.  I edited
matplotlibrc to change interactive: to "True".  In idle, I entered the
commands:
     >>> from pylab import *
     >>> plot([1,2,3])

The terminal window closed abruptly when I typed the closing
parenthesis.
I have been warned not to use the show() command in interactive mode.
I tried:
     oyinbo at oyinbo-laptop:~$ idle-python2.4 -n
In idle -n, I entered the sam two commands.  This time I got an error
message:
     The program 'idle-python2.4' received an X Window System error.
     This probably reflects a bug in the program.
     The error was 'BadWindow (invalid Window parameter)'.
       (Details: serial 2875 error_code 3 request_code 15 minor_code
0)
       (Note to programmers: normally, X errors are reported
asynchronously;
       that is, you will receive the error a while after causing it.
       To debug your program, run it with the --sync command line
       option to change this behavior. You can then get a meaningful
       backtrace from your debugger if you break on the gdk_x_error()
function.)

Using the Python prompt without idle, I got no error message, but the
window simply didn't open:

     oyinbo at oyinbo-laptop:~$ python
     Python 2.4.3 (#2, Mar  7 2008, 01:58:20)
     [GCC 4.0.3 (Ubuntu 4.0.3-1ubuntu5)] on linux2
     Type "help", "copyright", "credits" or "license" for more
information.
     >>> from pylab import *
     >>> plot([1,2,3])
     [<matplotlib.lines.Line2D instance at 0xb7bf04cc>]

Have I skipped a step?

Thanks for all the great information on your group.

Bill