the autoupdate in Fx 3.5.3 on OSX has managed to confused itself. the Help menu is stuck (and presumably has been for days) showing "Downloading Firfox 3.5.4...". it's grayed out and i can't select it like one normally can to see progress. Preferences -> Advanced -> Update -> Show Update History says "Installed on: October 27, 2009 22:36:58 Status: Update server not found (check your internet connection)". i've still got firefox running in this state in case there's something worth prodding, but the state is no longer pristine. i fired up a second copy using: -- #! /bin/bash export MOZ_NO_REMOTE=1 /Applications/Firefox.app/Contents/MacOS/firefox -P stock & unset MOZ_NO_REMOTE -- to see what the normal UI looks like and it immediately began to (successfully) download the update.
Closing old bugs as incomplete. If this is still an issue please file a new bug.