I too lost a game that way hundreds of turns in. The game started with 1.2, the bug occured with 1.3 opt-in (no, opting out didn't help).
I checked all the ships like the forum threads regarding this bug suggested, but no luck. I also declared war on everybody - I saw my ships move and the AIs attacked my fleets ... but at some point the turn still got stuck. So I suspect an AI ship is the cause.