Why are there exclamation marks instead of the Shivering Isles Portal?

I've just downloaded Shivering Isles on Oblivion Xbox 360. I can't wait to visit another realm! When I got the quest to investigate the secret portal, I traveled to the Bravil Stable and I saw a yellow blob up ahead. I went closer and then I saw this:

These yellow triangles with purple exclamation marks. That was where the portal was and now this! How do I fix these exclamation marks?

Solution 1:

That's usually a sign of graphical error. I suggest verifying that your download has no errors.

Solution 2:

I have Oblivion for PC and that error means the Shivering Isles DLC is not loaded like other files (such as mods or Knights of the Nine). I've never played Oblivion on Xbox so I don' t know if it has a DLC load list or something similar.