Just completed the College of Winterhold questline and got the Arch Mage Robes, also had picked up Morokei from the previous dungeon. I was at first able to put them on together and it would negate the Arch Mage hood and use the one given to you by wearing Morokei. Had to save and reload and after I did, this happened.

Hopefully this gets fixed because both together looks awesome.

http://imageshack.us/photo/my-images/100/2011111200043.jpg/

That is awesome...

Yup, I've got the same problem from time to time. Sometimes the mask renders, sometimes it doesn't.
I think the problem lies with the slots the robes and mask take. I intend to look into that once I get my hands on the CK.
However, if you save your game and go to the main menu, and load again, that usually fixes it for me.
Another fix is just to equip and requip the mask, this also seems to works very sporadically.
Hope this helps

-Star

Can you guys tell me where to find the mask? Or is that not allowed here?

Yeah, reloaded a few times and it's showing now.

And that particular mask is in Labarythiunn (definitely spelled wrong).