On the item maintenance & item categories pages:
Item categories are sorted only on category_id rather than on description. This is not critical, but as categories grow it becomes quite unwieldy.
When I bulk loaded item categories they were in alpha order, so the problem didn't appear until I added a new category, which should have appeared somewhere in the middle of the list, but the category_id was of course the next available number at the bottom of the list.
I haven't checked all the other places where category is used, but on the direct invoice page, items are CORRECTLY grouped within categories which are sorted by description.