Did you get the cutscene conversation with Marius as he is walking in? How about with the memory eater at the start of the path leading down to the arena?
You could try clearing the Xbox cache and load the save before entering the Hall of Echoes again, but the problem could be in the save itself.
In the dragon sections of the Hall of Echoes you can teleport back to the battle tower, but if getting the game to reload the area would help, then reloading the earlier save probably would have done the same thing.
Try emailing firstname.lastname@example.org, if you haven't already, with a description of the problem and maybe a link to this topic.