[CentOS] - problem with reboot or shutdown

hi all,

I have a problem with my CentOS 6.3 distribution
only when I restart or turn off the machine it does not restart
properly. remains in both cases black screen and then I do not
understand exactly what he's doing.

grub after I hit send and then darkness.
only after that forcement for a further time the power cycle then it works.

the kernel version is 2.6.32-279.14.1.el6.i686

where is the problem?
thanks in advance
cheers