Comment 39 for bug 58232

I reportet the bug to nvidia but they said:
"This is a known X server bug which is triggered when using Composite with Xinerama. You should report it to Ubuntu. The current workaround is to disable Composite or Xinerama."

This is not the answer I liked to hear. I also get the bug by using multi-gnome-terminal:

multi-gnome-terminal

Gdk-CRITICAL **: file gdkwindow.c: line 1406 (gdk_window_get_visual): assertion `window != NULL' failed.

Gdk-CRITICAL **: file gdkcolor.c: line 57 (gdk_colormap_new): assertion `visual != NULL' failed.
class: Config prefix: /MultiTerminal/Win-Config/

Gdk-CRITICAL **: file gdkwindow.c: line 1406 (gdk_window_get_visual): assertion `window != NULL' failed.
Gdk-ERROR **: BadDrawable (invalid Pixmap or Window parameter)
  serial 135 error_code 9 request_code 146 minor_code 5
Gdk-ERROR **: BadDrawable (invalid Pixmap or Window parameter)
  serial 136 error_code 9 request_code 55 minor_code 0