I to am using Arch but haven't found any references to this same crash other than "updating the package" there is no "update for libxul.so" precisely, but some of the other error messages when trying to launch firefox from cli were helpful - I had to update "icu" as someone already mentioned, but Firefox still wouldn't launch but new error message pointed to "sqlite" out of date, updated it.

pacman -Sy firefox firefox-adblock-plus firefox-noscript

pacman -S icu lib32-icu harfbuzz-icu

pacman -S sqlite lib32-sqlite

This seems to have solved problem, Firefox launches, slow to find websites but is working.

bill@arch-bill ~ % uname -a Linux arch-bill 3.17.4-1-ARCH #1 SMP PREEMPT Fri Nov 21 21:14:42 CET 2014 x86_64 GNU/Linux

I too am using Arch but haven't found any references to this same crash other than "updating the package" there is no "update for libxul.so" precisely, but some of the other error messages when trying to launch firefox from cli were helpful - I had to update "icu" as someone already mentioned, but Firefox still wouldn't launch but new error message pointed to "sqlite" out of date, updated it.

# pacman -Sy firefox firefox-adblock-plus firefox-noscript
# pacman -S icu lib32-icu harfbuzz-icu
# pacman -S sqlite lib32-sqlite

This seems to have solved problem, Firefox launches, slow to find websites but is working.

bill@arch-bill ~ % uname -a
Linux arch-bill 3.17.4-1-ARCH #1 SMP PREEMPT Fri Nov 21 21:14:42 CET 2014 x86_64 GNU/Linux