When I use this command:
yum groupinstall "GNOME Desktop Environment"

After it loaded a lot of things it writes:

--> Missing Dependency: httpd >= 2.2.0 is needed by package gnome-user-share-0.10-6.el5.i386 (base)
Error: Missing Dependency: httpd >= 2.2.0 is needed by package gnome-user-share-0.10-6.el5.i386 (base)
You could try using --skip-broken to work around the problem
You could try running: package-cleanup --problems
package-cleanup --dupes
rpm -Va --nofiles --nodigest
Regards.