I was still using 43 because of bug https://bugzilla.mozilla.org/show_bug.cgi?id=1243194 but after a series of crashes I surrendered to 49.0.2. Unfortunately, for reasons I'd like to know, scim does not start in that version. Scim is a input method editor for Linux. I use it for Japanese (mainly). * if I downgrade, scim works again * other applications have no problem * I tried starting with explicit environment variables, like GTK_IM_MODULE="scim" XMODIFIERS="\@im=scim" LC_MESSAGES="nl_NL" LANG="ja_JP.utf8" (didn't need them earlier, just to make sure) * my distro is Slackware, version 14 * scim is standard configured to start in Slackware, if LANG is a utf var (echo $LANG gives ja_JP.utf8) * Firefox starts without errors * I've tried restarting X and even rebooting Linux I'm back to Firefox 43. :-( (Update 2017年 1月 5日 木曜日 12:39:28): A security update was forced upon me, I'm now on 45.0.2, which has no longer bitmap support (see the bug mentioned above) but does still have support for scim. I'll check the most recent version of Firefox sometime later in virtualbox (downgrading when Firefox still does not work properly is a nuisance).