So, you are installing Oracle Enterprise Linux 6 update 5 and you select the Desktop group of packages. When the system is finished installing and finally boots, it hangs at certmonger. The certmonger daemon monitors certificates for impending expiration, and can optionally refresh soon to be expired certificates with the help of a CA.

Why this kills the Desktop if X isn’t installed is beyond me. For some reason the dependent packages don’t get selected by yum. To fix it, perform the following steps.

1) Reboot and press the spacebar key to enter the boot menu during system start-up.
a) When the Grub menu appears, press the ‘e’ key.
b) Scroll down to the line with kernel and press the ‘e’ again.
c) At the end of the line, the last word should be ‘quiet’. Right arrow key over to the end of the line and press spacebar once to add a space after the word ‘quiet’ and press the 3 key.
d) Then press the Enter key and then the letter ‘b’ to boot the system.

2) The systems will boot into text mode. Now, add the X Window System rpm’s.
> yum update
> yum groupinstall “X Window System”

3) Reboot the system and you should have a working desktop.
> shutdown -r now