Jerry,
I read the link, It didn't help me remove my attribute.
Mine doesn't have any related expression attatched to it for me to delete, but it still won't go.
I can't understand why a draft file is so much different to a part file since they are basically the same, I can remove attributes from a part file easily.
I even created some test part and test drwg files from Blank templates, I can add and delete attributes with no problem, and get no related expressions