Regardless of what's in your PPRuNe profile, it's your browser settings that govern cookies. Although there's no reason why the setting should have changed (unless you fiddled with it), check that you
are accepting cookies. Tools,Internet Options, Advanced, then scroll down a ways.
Also you can check that there actually is a PPRuNe cookie on your system. (Delete your temporary files first to reduce the number of entries). Tools, Internet Options, Settings, View Files and look for an entry something like <yourname>.pprune.
If both the above are true, then I have no idea what's up
