It was hanging around because of some old Artmatic vesion 1.2 files. The first problem was that the Type and Creator codes had gotten lost at some point. The second problem was that I had 181 of them to fix. The third problem was that the current version of Artmatic doesn't open these old files.
First I asked the UI folks if they had a version of Artmatic that can open 1.2 files and save them as the current format. They do, Artmatic 2.5.
Next I needed to bulk change all the type and reator codes, so that Artmatic would recongise them. I found Typeator from. First I used Artmatic 2.5 to save a reference file, and then you can drag and drop files onto Typeator. It pops a dialog box saying choose "a master file" and then it changes all the files. Magic!
I used Jing and did a screencast file to show you.
Next stage, how to convert those old files