[CentOS] After performing a reboot in VM (Virtualbox), log user on gnome not display the desktop.

After performing a reboot in VM (Virtualbox) which had been stopped, the
User logs in but does not display the desktop leaving only the background
image.
The services are all active, can access and use the VM via ssh, but the
Desktop died.
I do not know where to begin to solve this problem.
Any idea?

Thanks

-------------------------------------------------------------
Rudinei Dias