This has been cropping up once in a while around the game lately. Player’s helms are replaced with a blue and white checkered box sitting on the tip top of their head. Most of the time the issue happens if you use a model changer to edit your character’s appearence (like back before Burning Crusade when people could use game files to make themselves look like Blood Elves) or something of that nature. A complete reinstall is about the only sure fire way to fix the problem.
The checkerboard box models will appear if the data for that object is missing. All known objects should be linked. If you end up getting any types of Error 131s and/or more of those objects, you may have to reinstall the game.
The original issue is usually seen if someone used a model editor. Possible outcomes are checkerboard objects and error 131s in certain zones after applying patch 2.4.0. (src)
Recent Comments