Firefox 3.6.18 keeps updating to 4.0.1 even with updates turned off

Question

I have two people who are trying to use Firefox 3.6.18 to access webpages that aren't compatible with Firefox 4 or 5. This is from Mac OS 10.6.
We've turned off all the update features, but they still get updated to 4.0.1 (it's unclear when this seems to happen to them, but they haven't clicked anything to accept any upgrades).
I even tried to take away their write rights to the Firefox application, but it didn't work since the permissions inside the application package were still their defaults that give her write rights.
Instead of fusing with the rights on the application some more, I currently have one of them running Firefox from a disk image file which she has no write rights to. There should be no way she can get an update to that one, but it's a clumsy fix and not something I like to have as a solution.
First, WHY is Firefox updating to 4.0.1 in the first place? If this is an attempt to force people to upgrade, this is unacceptable.
Second, what could be causing this behavior and how can it be fixed?
After this latest update was forced on her, she loaded Google Chrome as a workaround. Needless to say, this isn't a good workaround you want users to use if you want Firefox to continue to be used.

Answer 1

Firefox when there is an update will tell you there is an update and ask you.
I have several versions of Firefox and a wagon load of profiles.
I was asked once on 3.6.18 to update to 4 or 5 and I said no, I was asked to update to 3.6.18 which is where you should be on 3.6.* and I accepted, and am not bothered nor has any update been forced yet from 3.6.* to 5.0. When 3.6 goes EOL (end of life), I will turn off the check for updates.
I am on Windows 7.
Maybe because you are 3.6.10, if you want to go to 3.6.18, I can provide directions, if you updates are stuck. Which they would be if you are at 3.6.10 that would be too much for the update to handle. If you want to update to 3.6.18 here are directions.
For those that really need an earlier version of Firefox, find your system and the Firefox version you want in releases, download and start the install.
* ftp://ftp.mozilla.org/pub/firefox/releases/
:or '''with the latest of version 3'''
* '''http://www.mozilla.com/firefox/all-older.html '''
: Note Mac OS X 10.4 user, and Mac OS X 10.5 users without Intel cannot upgrade to Firefox 4 or 5.
When reinstalling Firefox from a download, Firefox must be down once the installation starts. When the installation finishes, don't let the install start firefox for you. Instead end the install and start Firefox in your normal manner, thus preventing creating a new profile which does not have your bookmarks cookies, etc (but your old profile would still be around and would).
Note: Firefox must be down once the install starts.
Close Firefox with File>Exit. Then make sure Firefox is not running --
On Windows: check the "Processes" tab in the Windows Task Manager.
On Mac: Firefox > Quit then Command+option+Esc, if Firefox running use Force quit
Permission errors on Mac:
If you were getting permission errors on a Mac, download the latest
Firefox version, then uninstall and reinstall Firefox. Do not remove
your profile directories and files as they contain your settings,
bookmarks, history, extensions, passwords, and cookies.