Firefox changes default spell checker on every startup

[HangFire]

EDIT: Sorry, wrong sub-forum, should have been under 14.04. Mods, please move.

I just installed Kubuntu 64 bit last week and am really enjoying it.

This is not a Kubuntu problem per se, but every time I start firefox, it is using an English dictionary that is not US, and I have to change it to US manually. On next start-up, it's not US again. While I appreciate my Australian and UK friend's right to spell things as they please, I would also prefer that Firefox remember my preferences.

Any help would be appreciated.

Info: Settings->Locale->Languages Tab->Preferred Languages is set to American English.

Some info from the command line:

$ locale
LANG=en_US.UTF-8
LANGUAGE=en_US
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=

$ cat ~/.kde/env/setlocale.sh
cat: /home/user/.kde/env/setlocale.sh: No such file or directory

$ cat /etc/lsb-release 
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04.1 LTS"

$ dpkg --list | grep firefox
ii  firefox                                     33.0+build2-0ubuntu0.14.04.1           amd64        Safe and easy web browser from Mozilla
ii  firefox-locale-en                           33.0+build2-0ubuntu0.14.04.1           amd64        English language pack for Firefox
$

[HangFire]

After some experimentation I have narrowed down the problem to FF Sync. With 3 or more Sync'ed browsers in different locations, it seems impossible to set them all at once to the same language and not have one revert the rest. This bad behavior is consistant through both the old Sync and the recent one.