Why does yum fail for RHUI clients which are older than Red Hat Enterprise Linux 5.4?

Issue

• RHEL5.3(and older than this version) of RHUI client failed to yum command. RHEL 5.4 is working properly.

# yum repolist -d 10
Not loading "rhnplugin" plugin, as it is disabled
Loading "rhui-lb" plugin
Loading "security" plugin
Running "config" handler for "security" plugin
Config time: 0.030
Yum Version: 3.2.22
COMMAND: yum repolist -d 10
Installroot: /
Running "postreposetup" handler for "rhui-lb" plugin
https://server1.example.com/pulp/repos/.test.com/pulp/mirror//content/dist/rhel/rhui/server/5/5Server/x86_64/os/repodata/repomd.xml: [Errno 14] HTTP Error 404: Not Found
Trying other mirror.
https://server2.example.com/pulp/repos/.test.com/pulp/mirror//content/dist/rhel/rhui/server/5/5Server/x86_64/os/repodata/repomd.xml: [Errno 14] HTTP Error 404: Not Found
Trying other mirror.
Error: Cannot retrieve repository metadata (repomd.xml) for repository: rhui-rhel-5-server-rhui-rpms. Please verify its path and try again

]# yum update -v
"rhnplugin" plugin is disabled
Loading "rhui-lb" plugin
Loaded plugins: rhui-lb
Config time: 0.068
Yum Version: 3.2.19
COMMAND: yum update -v
Installroot: /
Setting up Package Sacks
Running "postreposetup" handler for "rhui-lb" plugin
https://server2.example.com/pulp/repos///content/dist/rhel/rhui/server/5/5Server/i386/os/repodata/repomd.xml: [Errno 14] HTTP Error 401: Authorization Required
Trying other mirror.
https://server2.example.com/pulp/repos///content/dist/rhel/rhui/server/5/5Server/i386/os/repodata/repomd.xml: [Errno 14] HTTP Error 401: Authorization Required
Trying other mirror.
Error: Cannot retrieve repository metadata (repomd.xml) for repository: rhui-rhel-5-server-rhui-rpms. Please verify its path and try again