firefox/thunderbird default to US Letter for papersize

Simon, you can report bugs from the web page, you just need to search and find the correct package first. But using "ubuntu-bug" tool is anyway better since it attaches relevant system information and logs.

Status changed to 'Confirmed' because the bug affects multiple users.

This bug also causes me problems with machines I support. The default should *always* be the system-wide settings that Ubuntu honour, and at the very least it should not reset during an 'upgrade'. This 'reset to US paper size' arrogance is a major irritation and causes problems for users who print and get nothing but an error message telling them to change paper size while blocking the network printers job queue until somebody clears it.

$ lsb_release -rd
Description: Ubuntu 10.04.4 LTS
Release: 10.04

$ apt-cache policy thunderbird
thunderbird:
  Installed: 14.0+build1-0ubuntu0.10.04.1
  Candidate: 14.0+build1-0ubuntu0.10.04.1
  Version table:
 *** 14.0+build1-0ubuntu0.10.04.1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ lucid-updates/main Packages
        500 http://gb.archive.ubuntu.com/ubuntu/ lucid-security/main Packages

$ apt-cache policy firefox
firefox:
  Installed: 14.0.1+build1-0ubuntu0.10.04.1
  Candidate: 14.0.1+build1-0ubuntu0.10.04.1
  Version table:
 *** 14.0.1+build1-0ubuntu0.10.04.1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ lucid-updates/main Packages
        500 http://gb.archive.ubuntu.com/ubuntu/ lucid-security/main Packages
        100 /var/lib/dpkg/status
     3.6.3+nobinonly-0ubuntu4 0
        500 http://gb.archive.ubuntu.com/ubuntu/ lucid/main Packages

        100 /var/lib/dpkg/status
     3.0.4+nobinonly-0ubuntu4 0
        500 http://gb.archive.ubuntu.com/ubuntu/ lucid/main Packages

Is this the right upstream bug report?: https://bugzilla.mozilla.org/show_bug.cgi?id=351913

I guess this is fixed in later Ubuntu versions, so upgrading to 12.04 LTS could be a solution.

Unfortunately (1) moving some machines to 12.04 is not an acceptable option due to the vast differences in user interface, and (2) it is still not right (as far as I can tell) with 12.04 as a recently installed test system when set up for UK preferences with an OKI network printer set for A4, both Firefox and Thunderbird still default to US Letter paper size.
Even more irritating is the behaviour when each upgrade of Firefox or Thunderbird, often for security reasons and not choice, changes the settings back - that is fundamentally broken behaviour and is the sort of old MS arrogance of "we don't care what you configured, we know best" by resetting user's preferences for no good reason. I don't know (yet) if they break this on upgrades for 12.04 as we have not really used/checked this on the test system.
Since 10.04 is supposed to be LTS and this bug is old, it should be fixed for 10.04. Also I doubt it is an OS-side problem but must be an application problem, most certainly the arbitrary reset of previously configured preferences must be!

Firefox and Thunderbird are upgraded to the latest release in all stable Ubuntu releases, so there's no need to upgrade to 12.04 to receive a fix in a later version. That bug is very old and 10.04 has had that "fix" for over a year now with the Thunderbird 3.1.x series. If this is still affecting people, it must be a different bug.

Err...sorry, that's not correct, Thunderbird 3.0.x and Firefox 3.5.x were based on the Gecko 1.9.1 branch, so 10.04 had those fixes in Firefox and Thunderbird since release, it must be a new bug.

Do you know where they store the page size setting?
Also is there any (easy) way to force apt-get or similar to 'upgrade' a package to see what is happening?
I wonder if the package comes with a default config file that is clobbering the user-configured file?

I also looked at the Windows version in a VM and it has no page size preference option, I presume as it is written to always take the selected printer's choice. So this is probably a Linux-only bug (though I can't rule out MacOS since I don't have a Mac to try)/

Looks like this has been known about, but nothing useful done to really fix it, for 10 YEARS now:

https://bugzilla.mozilla.org/show_bug.cgi?id=147419

about:support will show you modified preferences, I believe they are stored in your prefs.js file in the profile directory

Incidentally my setting is LANG="en_GB.utf8" so it is still an issue and not fixed, as per comment 73 in the above link.

Looking at the modified preferences shown by about:support I don't see anything that appears to be the global page size.
There are various printer-specific settings, but as this problem occurs with all printers it is clearly a program-wide problem and not a printer-specific one.

I'm going to mark this as a duplicate of bug 10910. This is an upstream issue and not an Ubuntu specific one. As you said, it's been broken upstream for about 10 years now. The person assigned last updated the bug about 3 years ago.

In fact, if I use the 'Copy all to clipboard' option to save a text file with the paper size as A4 and as US Letter, diff finds no differences. So basically the user's preference for this is not being saved in the usual manner. Maybe this is why it is clobbered on upgrades?
It is still not an excuse for defaulting to US Letter in the first place, when the environment (such as LANG="en_GB.utf8" in my case) is clearly for the European option, and not US.