I can never complete a quest without resorting to uesp.net console command. I have no mods that affect these quests or locations.
In Thieves Guild, Karliah will simply turn around and walk out of the cave instead of opening the gate. As she is the only one able to open it, this will render the quest impossible to complete. Solution, delete gate then setstage tg08a 52 to continue the quest.
Main quest, Esbern does'nt unlock the door. Solution, skip forward to the start of the next quest, http://uesp.net/wiki/Skyrim:Alduin%27s_Wall, by using the console and typing in setstage MQ203 5, which will allow you to continue. But his dialogue remains in the sewer so I can not continue the dragon hunt.
The Companions can't be cured when requested as they don't follow the player or emediately walk out the tomb with no dialogue.
The Storm Cloaks/Imperial, Battle for Whiterun, random CTD on the battle field. Main door, CTD use basemant door. Battle for Solitude/Windhelm, random CTD on the battlefield, CTD on activating main gate, so much for those questlines. Yet players still clammer for the next busted TES game?