collapsible dead after update, drupal.settings undefined

I have an old site I wanted to update on localhost.
I made a copy in a subfolder and configured etc/hosts and apache to use a fake TLD (togethearth.con instead of .com). So on my machine: togethearth.con -> 127.0.0.1/togethearth
settings.php is configured accordingly (togethearth.con) to keep clean URL.
I kept the SAME database for the 2 versions (5.10 and 5.16).

After I updated togethearth.con from 5.10 to 5.16 + updated modules, there's no more collapsible menus in SOME settings (taxanomy user roles, OGUR, FCKeditor, ...).

in FF3 (Minefield on Mac) error console, I have:
Error: Drupal.settings is undefined
Source File: http://localhost/modules/admin_menu/admin_menu.js
Line: 5

And also in Safari Error Console:
Undefined value

And the same database with 5.10 (and old modules) is working fine in both Firefox and Safari! No errors and all collapsible menus are working.

I also get (for both 5.10 and 5.16 on FF3):
Error: [Exception... "Component is not available" nsresult: "0x80040111 (NS_ERROR_NOT_AVAILABLE)" location: "JS frame :: file:///Applications/Minefield.app/Contents/MacOS/components/nsSessionStore.js :: sss_saveState :: line 1909" data: no]
Source File: file:///Applications/Minefield.app/Contents/MacOS/components/nsSessionStore.js
Line: 1909

Not sure if it's related.

Thanks for your help, and I hope it will help others.