Exactly the same problem. My phone and S2 tablet kept telling me my samsung session had expired, and that I needed to log in again. This started occurring about 5 days ago. When I try to log in, I go through the same rigmarole that Greensweeper describes, including unsuccessfully trying to turn off 2-step verification via web.
The issue seems to be with my Samsung tablet, as I can enter my account using my mobile internet after successfully going through two-step verification on there.
I get the impression that waiting on a proper solution via this community might be futile so if someone from Samsung could just provide me with a free/ normal rate number to speak to an account specialist to get this fixed, I'd be very grateful.
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