I also have the problem on version 34b from PPA

That crash has a signature which matches 49 reports during the past 28 days, all amd64-based systems running Linux (see https://crash-stats.mozilla.com/repor.../list?product=Firefox&range_unit=days&range_value=28&signature=libc-2.19.so%400x36d27#tab-sigsummary). It's a fairly rare crash and unfortunately not much information is available to the volunteers here from those reports.

The Safe Mode test ruled out the most common issues, so my next thought is to take the most common plugin out of the equation. You can set Flash to click-to-play so that sites can load without it. You probably will need to activate it to watch videos, but on those sites that only use it for analytics, advertising, and local storage, you might not need to activate it.

To conduct this test, open the Add-ons page. Either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Plugins. Then find "Shockwave Flash" and change the default permission to "Ask to Activate".

When you visit a site that wants to use the Flash, you should see a notification icon in the address bar and one of the following: a link in a black rectangle in the page or an infobar sliding down between the toolbar area and the page.

I suggest keeping Flash disabled as much as possible until you determine whether it is making any difference. Does it?

Disabling plugins (even all of them) doesn't help, I'm afraid.

Do Gmail and Guardian get far enough to display a plugin approval notification, or crash before that point?

Hopefully a Linux expert will recognize something in your crash report(s) that I don't see.

You can try to disable OMTC and leave hardware acceleration in Firefox enabled.

• about:config page: layers.offmainthreadcomposition.enabled = false

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

You can also try to disable GStreamer support for the HTML5 media player.

• about:config page: media.gstreamer.enabled = false

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

jscher2000 : I was concentrating on the gmail issue where there was no visible plugin request. I did finally find a crashing grauniad page and yes - I did need to approve the plugin to play.

cor-el : The bad news is that OMTC was disabled BUT disabling Gstreamer support seems to have done the trick so you probably get the cigar. I shall continue to test before marking as solved.

I nearly missed libgstlibav.so in the crashing thread.

• bp-cefad394-2054-4c5a-b2f0-d4da42141130

Make sure that you have the latest updates for GStreamer.

I am rather at the mercy of the packagers here but am up-to-date for the distro.

Thanks both for the amazing quick responses.