Maybe its for older Firefox-versions since i dont understand/find:
2. The cure;
1) (i) Go to settings (the cog on the tool bar at the top of the page), (response will be slow until the problem is fixed, so give it time)
(ii) Select Privacy settings,
(iii) Select security,
(iv) Select edit active sessions,
(v) Close all active sessions except one.
2) Un-click the "stay logged on" button at log-in.
3) "Log out" before exiting Facebook each time.
4) Periodically check the number of active sessions.
WHERE ARE THESE ACTIVE SESSIONS?
Thanks

Yes the problem is on my old Winxp with non-SSE-processor.
Its from here:
https://www.facebook.com/help/commun...51469026437322
many hints. e.g.
ipconfig /flushdns