It seems to solve this problem I have to uninstall yum and reinstall it.
If I try that it returns this:
rpm -e yum
error: Failed dependencies:
yum is needed by (installed) yum-conf-1.0-101.rhe5x.iworx.noarch
yum >= 3.2.19-16 is needed by (installed) yum-utils-1.1.16-14.el5.centos .1.noarch
yum >= 3.0 is needed by (installed) yum-fastestmirror-1.1.16-14.el5.cent os.1.noarch
yum is needed by (installed) interworx-4.3.0-299.iworx.noarch