Unable to plot simple matplotlib figures


I installed matplotlib from source in Mac OS 10.6. However, I am unable to print this simple example plot:
from pylab import *

Here is what I get when I try using TkAgg as the backend:

casa98-125-dhcp:.matplotlib lisa$ python simple_plot.py --verbose-helpful
matplotlib data path /Users/lisa/.local/lib/python2.6/site-packages/matplotlib/mpl-data
loaded rc file /Users/lisa/.matplotlib/matplotlibrc
matplotlib version
verbose.level helpful
interactive is True
units is False
platform is darwin
Using fontManager instance from /Users/lisa/.matplotlib/fontList.cache
backend TkAgg version 8.5
Traceback (most recent call last):
  File "simple_plot.py", line 2, in <module>
  File "/Users/lisa/.local/lib/python2.6/site-packages/matplotlib/pyplot.py", line 2134, in plot
    ax = gca()
  File "/Users/lisa/.local/lib/python2.6/site-packages/matplotlib/pyplot.py", line 582, in gca
    ax = gcf().gca(**kwargs)
  File "/Users/lisa/.local/lib/python2.6/site-packages/matplotlib/pyplot.py", line 276, in gcf
    return figure()
  File "/Users/lisa/.local/lib/python2.6/site-packages/matplotlib/pyplot.py", line 254, in figure
  File "/Users/lisa/.local/lib/python2.6/site-packages/matplotlib/backends/backend_tkagg.py", line 91, in new_figure_manager
    canvas = FigureCanvasTkAgg(figure, master=window)
  File "/Users/lisa/.local/lib/python2.6/site-packages/matplotlib/backends/backend_tkagg.py", line 158, in __init__
    master=self._tkcanvas, width=w, height=h)
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-tk/Tkinter.py", line 3284, in __init__
    Image.__init__(self, 'photo', name, cnf, master, **kw)
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-tk/Tkinter.py", line 3240, in __init__
    self.tk.call(('image', 'create', imgtype, name,) + options)
_tkinter.TclError: integer value too large to represent

I've tried the MacOSX backend and that opens a GUI that has the label Figure 1 but no plot. Saving to a post script file does not work either. Does anyone know what the problem is?