If you want to try to get rid of buzz on the affected account,
this tells how.
I'm looking through recent bugs seeing more for different add-ons/plugins and contacts.
ETA: Not seeing anything specific to your problem that would be recent. There's other, older bugs that have been fixed/sort of fixed, though.
You might try stripping your profile down to basics, remove any sort of extras you have, and change the UI to an older one? If that solves the login/out issue, slowly start adding stuff back.

In a situation where you can't see any sort of error log, trial and error is about all you have.