Comment 8 for bug 211954

Hmm, there's a couple interesting bits in your .xsession-errors file, one relating to CRTC assignments and monitors, the other relating to usershares. I'm guessing the former may be the main suspect. From the error messages it sort of sounds like Compiz is involved; I'll add that as a possible component in case the compiz folks recognize the issue.

Computed CRTC assignment in 0.00 ms
 ... no assignment found
ALSA lib control.c:909:(snd_ctl_open_noupdate) Invalid CTL front:0
ALSA lib control.c:909:(snd_ctl_open_noupdate) Invalid CTL front:0
Shutdown failed or nothing to shut down.
...
/usr/bin/compiz.real (core) - Warn: Unable to parse XML metadata from file "ccp.xml"
Initializing nautilus-share extension
11

** (nautilus:6350): WARNING **: Unable to add monitor: Not supported
...

Starting gtk-window-decorator
/usr/bin/compiz.real (video) - Warn: No 8 bit GLX pixmap format, disabling YV12 image format
Nautilus-Share-Message: Called "net usershare info" but it failed: 'net usershare' returned error 255: net usershare: cannot open usershare directory /var/lib/samba/usershares. Error No such file or directory
Please ask your system administrator to enable user sharing.

I/O warning : failed to load external entity "/home/whoop/.compiz/session/default0"

(gnome-panel:6349): Gtk-WARNING **: gtk_widget_size_allocate(): attempt to allocate widget with width -12 and height 24