The value of spellchecker.dictionary should be "en-US" for the en-US dictionary and not have an underscore.

• user_pref("spellchecker.dictionary", "en-US");

Do you have a user.js file in the profile folder that might override the last saved setting in prefs.js?

Thanks for the reply. I changed the prefs.js file manually to "en-US" (with FF closed) and started FF. It's checking spelling in Australian. I should point out that FF uses an underscore when it rewrites that line in prefs.js.

I do have a user.js file, but it contains only two lines relating to Picassa, and in particular nothing about the spelling language.

Maybe that is caused by the way the Ubuntu has branded that version.

You can try Firefox from the official Mozilla servers to see if it still happens.

• Firefox 9.0.x: http://www.mozilla.org/en-US/firefox/all.html

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.org/kb/Safe+Mode

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Thanks, but I'm already using an unbranded version of FF.

I've got a workaround: I turned off "preferences" in the Sync settings. Best guess is that FF upgrades revert to en_AU, and that gets "stuck" in the Sync memory. I tried changing the setting to en_US and then forcing a sync, which didn't work -- not sure if the sync failed or what. After I've got every copy of FF back to en_US, maybe I'll try syncing preferences again.

If it's really upgrades that are switching me back to Australian, I would call that a bug. Upgrades should respect whatever preferences the user has set in his/her profile.

I appreciate the suggestions.

Paul

That workaround turned out not to work, although I'm not sure why. I turned off preference syncing, adjusted the language to en_US, and restarted FF. The language setting survived the restart. Opened FF this morning, though, and it had reset to Australian. <sigh>

So I deleted the Australian English dictionary from Hunspell (sudo rm /usr/share/hunspell/en_AU.*), and hopefully FF will now wake up using the US dictionary. I discovered, though, that something had added symlinks in the folder to make en-AU.* aliases for en_AU.* files. I wonder if that had anything to do with Firefox grabbing the Australian dictionary at startup?