Redhat Linux yum grouplist and groupinstall Option Not Working

I'm trying to install all the default packages by group using 'yum groupinstall groupname' command under RHEL v5.x. But, grouplist, groupinstall, and groupdelete options are not working with yum. How do I fix this issue and make sure yum command works with software groups under Redhat Enterprise Linux to increase my productivity?

You need to install a package called yum-utils. It is a collection of utilities and examples for the yum package manager. It includes utilities by different authors that make yum easier and more powerful to use. These tools include: debuginfo-install, package-cleanup, repoclosure, repodiff, repo-graph, repomanage, repoquery, repo-rss, reposync,
repotrack, verifytree, yum-builddep, yum-complete-transaction, yumdownloader, yum-debug-dump and yum-groups-manager.

Install yum-utils

Type the following command:
# yum install yum-utils
To list software groups enter:
# yum grouplist
Sample output:

Loaded plugins: rhnplugin, security
Setting up Group Process
Installed Groups:
   Engineering and Scientific
   Graphics
   Network Servers
   System Tools
Available Groups:
   Administration Tools
   Authoring and Publishing
   Development Tools
   Editors
   Educational Software
   FTP Server
   Fedora Packager
   GNOME Desktop Environment
   GNOME Software Development
   Games and Entertainment
   Graphical Internet
   Hardware Support
   KDE (K Desktop Environment)
   KDE Software Development
   Mail Server
   News Server
   Office/Productivity
   Sound and Video
   Text-based Internet
   Web Development
   Web Server
   Window Managers
   X Window System
Done

To install "Web server" group, enter:
# yum groupinstall "Web server"