I'v set up an Ubuntu 12.04 from the precreated OpenVZ template. The host system is configured as follows:

# $ cat /etc/issue
Debian GNU/Linux 6.0

# $ uname -a
Linux openvz-02 2.6.32-16-pve #1 SMP Fri Nov 9 11:42:51 CET 2012 x86_64 GNU/Linux

# $ apt-cache showpkg proxmox-ve-2.6.32
Package: proxmox-ve-2.6.32

# $ tail -n 3 /etc/apt/sources.list
# PVE packages provided by proxmox.com
deb http://download.proxmox.com/debian squeeze pve

For a software project I need a minimal xserver and followed the instructions at https://help.ubuntu.com/community/ServerGUI. I simply installed the package xorg (xorg 1:7.6+7ubuntu7.1).

Now when I 'startx' I get an error message

Fatal server error:
xf86OpenConsole: Cannot find a free VT: Invalid argument

The complete output of startx

# startx


X.Org X Server 1.11.3
Release Date: 2011-12-16
X Protocol Version 11, Revision 0
Build Operating System: Linux 2.6.42-23-generic x86_64 Ubuntu
Current Operating System: Linux www 2.6.32-16-pve #1 SMP Fri Nov 9 11:42:51 CET 2012 x86_64
Kernel command line: quiet
Build Date: 29 August 2012  12:12:33AM
xorg-server 2:1.11.4-0ubuntu10.8 (For technical support please see http://www.ubuntu.com/support)
Current version of pixman: 0.24.4
    Before reporting problems, check http://wiki.x.org
    to make sure that you have the latest version.
Markers: (--) probed, (**) from config file, (==) default setting,
    (++) from command line, (!!) notice, (II) informational,
    (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: "/var/log/Xorg.0.log", Time: Tue Nov 20 08:46:04 2012
(==) Using system config directory "/usr/share/X11/xorg.conf.d"

Fatal server error:
xf86OpenConsole: Cannot find a free VT: Invalid argument


Please consult the The X.Org Foundation support
     at http://wiki.x.org
 for help.
Please also check the log file at "/var/log/Xorg.0.log" for additional information.

 ddxSigGiveUp: Closing log
Server terminated with error (1). Closing log file.