it will be something to do with the cookies and some recent issues/changes that go on.
Personally I don't use it, so am unfamiliar with it all.
However, take a look at the UCP, and look at the Profile tab. There is a Manage “Remember Me” login keys section, where you can delete certain keys.
Possibly you could try deleting all of yours and starting again to see if that makes a difference.
Offer ideas and suggestions on how you think this forum can be improved.