rhel 6 hangs out after atd service status ok durning system bootup
 

In Rhel6.0 bootup,All the services states starting OK till Atd status OK .
then screen hangs out.
actually some problem regarding gnome was display on the screen but i ignore it now i am not able to run in runlevel 5 however i can run in runlevel 3
i tried this command yum --releserver=6.4 upgrade but doesnot work out

Your problem is that the GNOME desktop is not starting. If you tell us what error you are getting, somebody may be able to help you.

As regards upgrading to RHEL6.4, unless you have a Red Hat subscription for your system, you are not going to be able to upgrade to 6.4