I need some hlp with the Ultimate Heist on Oblivion.?

you know when you get into the Elder Scrolls Library with the Blind Moths? and hows there is a "Reading Chair" that you have to sit in so you can get the Elder Scroll? yeah, well for some reason its not letting me sit in that chair. i can sit in any other chair, but that one. please help, this problem is getting kinda annoying.