Can't Save - Archmage Rezo

[Throwaway]

Got Steam Version, Win7 64.

After defeating the Staff of Destruction in the Archmage Rezo quest i can't save the game.

To be more specific, after the fight the staff doesn't disappear and the fight begins again; Right at the beginning of the second fight Rezo begins the post-quest dialogue; Following the dialogue options gets me out of the tower but i can't save.

After some search it seem this bug is quite old, but i couldn't find any solutions. Help is appreciated.