Yum not working after upgrade

[Colin Paul Adams]

Yum is not working after I upgraded from F10 to F11.

yum update

gives me:

here 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:
2.6 (r26:66714, Mar 17 2009, 11:44:14) 
[GCC 4.4.0 20090313 (Red Hat 4.4.0-0.26)]

If you cannot solve this problem yourself, please go to 
the yum faq at:
  http://wiki.linux.duke.edu/YumFaq

rpm -q yum gives me:

yum-3.2.23-3.fc10.noarch

so it looks like it wasn't upgraded.

How am I supposed to fix this by hand?
-- 
Colin Adams
Preston Lancashire