I've the same problem, it happen often when I log in GNome first time and then sometimes when I'm using VmWare and switch from Vm and host (physical machine).
$ ubuntu-bug xorg
--> [5569:5569:0114/073520:ERROR:nss_util.cc(819)] After loading Root Certs, loaded==false: NSS error code: -8018
ATTENTION: default value of option force_s3tc_enable overridden by environment.
Created new window in existing browser session.
I've the same problem, it happen often when I log in GNome first time and then sometimes when I'm using VmWare and switch from Vm and host (physical machine).
$ ubuntu-bug xorg 0114/073520: ERROR:nss_ util.cc( 819)] After loading Root Certs, loaded==false: NSS error code: -8018
--> [5569:5569:
ATTENTION: default value of option force_s3tc_enable overridden by environment.
Created new window in existing browser session.