Playing on the latest SVN revision earlier today, I ran into some unexpected difficulties when attempting to begin a campaign as the Ottomans. The Byzantine Empire had collapsed before my spawn, leaving Constantinople as an Independent city garrisoned by a lone longbowman. The city's immediate capture seemed imminent, but since I had spawned inside its borders, my units harmlessly moved into the city instead of capturing it.
What was interesting was that in the normal game view, my units appeared to be in an empty tile, culture-wise. But when I went to World Builder, surely enough, my units were standing in the city's territory. I unfortunately don't have the save file for that attempt, but my latest attempt is also suffering from a bug.
The second time around, things went much more swimmingly, as Constantinople was a Holy Roman city, allowing me to declare war through the diplomacy screen. However, after a while, I realized that all of my stability values were at 0, and had been for the whole game. Has stability been disabled again?