RHEL hangs after upgrade

Hi techies,

We have upgraded our system from RHEL 6.1 to 6.6 . After up gradation during booting with new kernel system hangs with below last messages
"Starting jexec serviceStarting rhsmcertd....."

However we can able to ping the server and ssh also. We have tested upgradation on multiple system but everytime got same result.

Can you put some light on it.