yum fails with "[Errno 4] IOError: <urlopen error (111, 'Connection refused')"

Issue

• Yum fails with errno 4 connection refused when trying to check for updates

Error: failed to retrieve repodata/e072654d542e3315689b37cfe5b3eb043cc73657-primary.xml.gz from rhel-x86_64-server-5
error was [Errno 4] IOError: <urlopen error (111, 'Connection refused')>

• Error from yum when trying to install package updates for rhel server

Error Downloading Packages: 
  krb5-libs-1.6.1-36.el5_4.1.i386: failed to retrieve getPackage/krb5-libs-1.6.1-36.el5_4.1.i386.rpm from rhel-i386-server-5 
error was [Errno 4] IOError: <urlopen error (111, 'Connection refused')>

• rhn_register or rhnreg_ks fail to register a system with the error Errno 4, IOError