I faced this error:

Unable to open /proc/vz/veinfo: No such file or directory

And what is the idea?
You might not be booted into OpenVZ kernel. Open this topic: http://internetlifeforum.com/virtualisation/170-installing-server-vps-reselling-hypervm-hypervisor-openvz-x-xen/
and find "check grub boot loader" on that page. and follow instructions to check /etc/grub.conf file and reboot if was incorrect boot order.