From the PTCUser portal, http://portal.ptcuser.org/p/fo/st/thread=41561&per=10&sort=0&p=1
Actually to "logout" of Windchill requires the browser to forget the
user name and password. Recent versions of Firefox have this ability under:
Tools | Clear Recent History and then make sure you only select
"Active Logins"
Or you can download the "Web Developer" addon for FireFox which provides
this functionality (and a whole lot more) under:
Miscellaneous | Clear Private Data | HTTP Authentication
FireFox also give one the ability to run multiple profiles so you can
be logged into a given website (such as your Windchill install) as
different users at the same time.
OR
There is no need to close all the Tabs if you are using FireFox
to log out using Firefox you can use "Ctrl+Shift+Del" or "Tools | Clear Recent History" then refresh the page "F5" FireFox will prompt for user name and password, once you log in as a different user you have that users access permissions in all of the open "Tabbed Pages"