sorry if my english is bad. This problem happened to me 3-4 times, but i only remember last time. It was very late for me so my memory can be wrong. My time setting is UTC -5:00, and it happened between 1h00-4h00 AM. It's hard to say because i'm usually logged for long period of time. I'll take note of that and write down the time it happens again.
Also would you be interested in a list of problems or something i (or the community) can help for the Steam release, because i want to help but i'm not sure how.