[Game breaking bug in the forgotten sanctum]

I have encountered a game breaking bug in the Forgotten Sanctum under the Black Ilses. 

When i go from the Sciptorium to the Temple of recollection talk to Tayn after completing his "a shout..." quest the game plays a scene where he argues with an imp. 
When the scene ends nothing happens. 
No keyboard
no mouse 
no HUD

just stuck. All the animations still work. 
I then have to ctrl+alt+delete to quit the game
When i reload the game it shows a message in the top right corner just before the load screen starts (maybe it's relevant - see black image)
I've noticed the game seems unstable after the latest massive update to Steams UI but i do not know if that is just a coincidence (the load screen flickers quite a lot and the whole sanctum area have seemed a bit unstable. for example: in battle sometimes error messages will appear instead of the normal red damage counters) 

I have run a file integrity check via steam and the game should be updated with the latest patch.

please help! i've played almost 130 hours and i absolutely love this game!  

regards
Bear