Just installed VO, after the update is complete and I click play vendetta, it closes and will not open the game. After trying to run from the terminal I get this error message repeatedly:

Xlib: extension "GLX" missing on display ":0.0".
Fatal Error: Couldn't open window.

As well as this at the beggining of the string of errors.

(update.rlb:1867): Gtk-CRITICAL **: gtk_text_buffer_emit_insert: assertion `g_utf8_validate (text, len, NULL)' failed

Any ideas?

You don't appear to have OpenGL working, which is what Linux uses for 3d graphics. Make sure you have it installed (probably a package named "libgl" or "opengl" or something along those lines), and if so, make sure you have Xorg configured to use it. You may need a 'Load "glx"' line in the module section of your /etc/X11/xorg.conf file if you have an older version of Xorg, but it doesn't seem to be necessary with the new ones. I don't have one anyway.

If you still get the error, examine your /var/log/Xorg.0.log file and find out why it isn't working.

Your distro of choice should have some kind of documentation about this with more specific instructions.