[Yum] Yum problem

[root]

my problem : no module named yum, my flavor RHELv4. solve it pls.
Mail address: sah at dhaka.net
There was a problem importing one of the Python modules
required to run yum. The error leading to this problem was:

   No module named yum

Please install a package which provides this module, or
verify that the module is installed correctly.

It's possible that the above module doesn't match the
current version of Python, which is:
2.3.4 (#1, Nov  4 2004, 14:06:56) 
[GCC 3.4.2 20041017 (Red Hat 3.4.2-6.fc3)]

If you cannot solve this problem yourself, please send this
message to <yum at lists.linux.duke.edu>.
This message display when i type yum