Hello,
Many people including me do experience issues running gnome on X.org after recent upgrade to Arch linux.
Most people report it's a GDM thing. For me it looks as if it might also something to do with nvidia drivers.
Here is the arch linux bug:
https://bugs.archlinux.org/task/56172I apologize for off topic, however I'd say it's at least marginally relevant since depending on your setup you might render your system inaccessible if you won't do the upgrade with some extra care at this time.