ERROR: No module named _tkinter

[Thomas Gagne]

tgagne:/home/tgagne/tmp/idle-0.5 ./idle.py
Traceback (innermost last):
  File "./idle.py", line 2, in ?
    import PyShell
  File "./PyShell.py", line 12, in ?
    from Tkinter import *
  File "/usr/local/lib/python1.5/lib-tk/Tkinter.py", line 8, in ?
    import _tkinter # If this fails your Python may not be configured for Tk
ImportError: No module named _tkinter

What do you suppose the problem is?