I've completed the Thieves Guild main questline (Darkness Returns) and chosen my special power (Shadowcloak of Nocturnal). It says completed in my quest log.
I also completed the extra jobs in each city you can give Thieves guild influence to (Markarth, Whiterun, Windhelm, and Solitude) and done their special jobs from Delvin. They show completed in my quest log. I've even done at least one of each kind of job from Vex and Delvin (but not in each city).
I got 4 vendors in the Ragged Flagon and have done the quest for Tonilia (delivering the Moon Sugar to a caravan) and Vekel (getting the 4 books). I've also upgrade one of my pieces of Thief Armor.
I talk to Brynjolf to become guild master and I get no dialogue options but he just says he's busy and we'll talk another time. There is a guild chest in front of his desk but it's locked and I don't have the key.
What am I missing? Is there some bug I've encountered?