Hi,
I had the same problem. The issue is the X-win server will not start because Parallels tools breaks the framebuffer with the RHEL 6.4 update. This is especially easy to see because a fresh install works fine until you install Parallels tools.
When you see the "select system to boot" message, hit the key that allows you to edit the boot arguments. Add a "3" to the end to force the startup to runlevel 3 (which is a console login without the GUI).
After logging in, type the command "startx" and you will see that it fails. Once you are able to fix this problem, the normal bootup into the GUI login will also work.
I had to downgrade the video driver subsystem back to 6.3 for it to start working, and you also have to add an exclusion to yum to prevent it from updating and removing the fix. This will be necessary until Parallels releases an updated tools that addresses this issue. There is a procedure I found in the CentOS forums for how to do this, sorry I don't have the link.
I put in a support ticket and their answer was "RHEL 6.4 not supported". I responded this is not the right answer and to tell me when it will be fixed and what versions of parallels. At present, I have asked this ticket to be escalated so hopefully someone can give us an idea of when they will fix this. I have a hard time believing they are simply going to stop supporting RHEL.
Last edited: May 18, 2013