centos yum 没法用了。

centos yum 没法用了。
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:
2.4.4 (#1, May 14 2013, 16:27:47)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-3)]
If you cannot solve this problem yourself, please go to
the yum faq at:
http://yum.baseurl.org/wiki/Faq
vim yum已经修改，python2.7也是同样的问题。我的系统是centos 会不会哪里的Red Hat 4.4.7-3有问题啊。