I can confirm this bug. It does occur intermittently - seemingly at random on my desktop but never on my laptop.
Like the original poster's, my xsession-errors contains these warnings:
gnome-session[6520]: WARNING: Application 'gnome-wm.desktop' failed to register before timeout
** (nautilus:6682): WARNING **: Unable to add monitor: Not supported
but nothing else last time I checked.
I can confirm this bug. It does occur intermittently - seemingly at random on my desktop but never on my laptop.
Like the original poster's, my xsession-errors contains these warnings:
gnome-session[ 6520]: WARNING: Application 'gnome-wm.desktop' failed to register before timeout
** (nautilus:6682): WARNING **: Unable to add monitor: Not supported
but nothing else last time I checked.