- Are you guys using multi-threaded gl ? Not here. We could be if Frederic was 1) using non-default preferences such as layers.acceleration.force-enabled and 2) viewing specific Web pages (e.g. using WebGL). But here we are talking about a startup hang occurring before this could kick into play. Frederic, can you say if you have any force-enabled prefs set in about:config? - Considering that the problem is not available with a standalone glxtest app, do you have a link to a FF build that one can test against ? Sure. You need a Nightly build, but not a current one since we have landed a work-around (avoiding to call XCloseDisplay here). This one, from Feb. 20, should reproduce: http://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/2014-02-20-03-02-02-mozilla-central/ E.g. http://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/2014-02-20-03-02-02-mozilla-central/firefox-30.0a1.en-US.linux-x86_64.tar.bz2