Hi there.
It should show the category, there are options in the plugin params to control what it draws when it finds a category ingredient. At least one of the options has it scroll through a list of ingredients of that category, so the issue might be one of the ingredients it's finding being bugged or something.
I think what's likely happening here is that it's set to show the category name with an icon, but the icons weren't set up in the plugin parameters, so the window can't draw the icon because the length of the list is undefined.
That error could also be caused if you're using an old save, as well. Since the icon list might be tied to the save file or something. There's always something screwy going on when you use an older save file.
~Ramza