Hi, I recently started playing Oblivion, and I like it. But I got a problem:

I'm making the main quest, and I'm at the point were I need to speak to Baurus at the "Luther Broad's Boarding House".
Here comes the problem, as soon as I enter the Inn, the game slows down / lags amazingly. And Baurus appears just in underpants.
The whole time I'm in the same room as Baurus, or in the same.. "map", the game is slowed down. And as far as I know, I need to go to the sewers with him, but walking through the Imperial City with him is impossible, it is impossible to play this way.

Please, why is this happening? I restarted the game 3 times to see if it was the save or something, but each time the same

Please, help me.

Do you have all the updates? How many hours on that save?