See my other comment. Because I try to document as much as possible of what I install / configure, I have been running Firefox for a while fresh out of the box. I didn't have this problem on 10.04 with an older version of Firefox (except for multimedia crashes). I am currently running 31.0. Links to recent crash reports follow. A quick peek gives me the impression that it's memory allocating/freeing related.
I've ran memtest86 for hours already, all is well. Which is not a surprise because the 8G installed is less than 2 years old, rest is less than 7 years old. I've already done a reinstall of 14.04 which is LTS. I've also checked for file corruption by using rsync with the -c (checksum) flag.
The app that chrashes the most is Firefox, followed by Thunderbird. I've checked several of the crash reports of Firefox. Some of those are in Mozilla's top list and have been there for a while. So I doubt it's flakey hardware (been running 10.04 . Like someone else suggested, I do have a lot of tabs open. But I've been doing this for years. If this is the problem, it's a recent one. Didn't have this many issues with 10.04, which I have been running until mid-2014.
Ubuntu 14.04 user here. Every time I login I am greeted with a stack of "System problem detected" warnings. Both Firefox and Thunderbird are extremely unstable. Firefox crashes a few times a week. Thunderbird does so twice a week (about). Now and then the whole system hangs when doing a rsync to an external disk (hangs, not busy).
Oh, I am sure Linux apologists blame me, my hardware, etc. But I've been running 10.04 for years on the same hardware, except that I replaced the 320G HDD for a 1TB one and switched to AHCI. Maybe that's the problem?
One issue I see often is this one: https://bugs.launchpad.net/ubu... It gives a very unfinished/unstable feel to 14.04