Comment 13 for bug 1518411

Also experiencing this currently on Ubuntu 16.04.5 LTS.

After working on the computer for a few hours, I can no longer open any application (Nautilus, Terminal, etc).

If I already had a terminal open before the issue occurs and I try to start nautilus from this old terminal, I get the following error:

Maximum number of clients reached
** (nautilus:29162): WARNING **: Could not open X display
sys:1: PyGIWarning: Nautilus was imported without specifying a version first. Use gi.require_version('Nautilus', '3.0') before import to ensure that the right version gets loaded.
/usr/share/nautilus-python/extensions/nautilus-admin.py:18: PyGIWarning: GConf was imported without specifying a version first. Use gi.require_version('GConf', '2.0') before import to ensure that the right version gets loaded.
  from gi.repository import Nautilus, GObject, GConf, Gtk, GLib
** Message: Init Stock Icons
Maximum number of clients reached
(nautilus:29162): GnomeDesktop-WARNING **: Unable to open display ':1' when setting background pixmap

Segmentation fault (core dumped)

I tried all possible solutions that were provided by Google but nothing worked. Restarting the system or closing half of the opened applications (e.g. Chrome tabs) seems to resolve the issue temporarily, but this is not really a solution but a workaround.