We upgraded to ITS 6.20 PL20 here with R/3 4.7 and in both IE 6 SP2 and Mozilla Firefox 18.104.22.168 sessions are terminated after a message "Session not fail-safe" appears in the status bar of the browser (the message actually only appears in IE, not in Firefox. Session is terminated all the same though). The usual "Invalid Session
You have tried to use a WWW session that has already been terminated." is displayed.
If someone could point me into the right direction, please.