I just met this problem ... On the internet to find a lot of posts, tried n methods are not successful ~
Then inspiration Flash, in the boot process press the up and down key, there appears the selection of the kernel version of the interface (do not press do not show),
Found there are two versions, because the default will go to compare the new version, so I manually selected the second, incredibly successful.
The problem is found, because some unknown operation, resulting in a more than one kernel option to boot, then remove the problem kernel or change the default boot on it.
I chose to remove the unwanted kernel,
Look at all the kernels, there are 6, 7, find the problem kernel,
enter sudo yum remove kernel-2.6.32-696.20.1.el6.i686
Delete the failed kernel. I reserve the rest for the time being.
Restarting the virtual machine succeeded. This is a direct entry into the normal system.