Did you by any chance touch one of the tombs? Because then the quest is broken... <img src="/ubbthreads/images/graemlins/disagree.gif" alt="" />sorry, if that's the case, hope you have another savegame.
I think this is fixed in the latest patch (1.34 I believe). You should probably download it and try again. Maybe the safer thing is to update your game, revert to an older savegame, try to stand in the circle again and see if that helps.
