Since March, I'm witnessing a constant need to login to my unified Wikimedia account. It appears whenever I restart my computer or restarts a web browser (any marque of browser). Sometimes it even happens inside an active editing session. Sometimes the system reports my being logged in centrally ("You only need to reload the page to reload your user preferences"). The problem appears at both my computers, using different flavours of OS X (10.6.8, 10.8.5).
In the past the system login sessions worked reasonably well at both my computers (I almost never log out, for ease of use). This logout behaviour started in March this year. During this spring lots of other users at my homewiki (Swedish Wikipedia) have reported the same or similar problems. Eg. here: https://sv.wikipedia.org/wiki/Wikipedia:Bybrunnen#HTTPS
This problem arises at all WMF projects. I suspect a problem of the system recognising a cookie could be the culprit?