ListBox Grouping and Virtualization

I would like to give a big “Thanks!” to Microsoft’s Ben Carter for providing me the high-level solution to this difficult problem, and making work over the past month a little bit less frustrating.
Update 3/3/2008: I have reworked my solution to prevent virtualization from not working when sorting the ListBox with the CollectionView sort descriptors. [...]

WTF Moment: Data Binding Errors in ListBoxes

Let’s say you have a ListBox that is data-bound to an ObservableCollection and set up similar to this:

Also, assume you’ve implemented sorting on your collection using the CollectionView representing your data bound items.
Can you guess what’s wrong?
When you sort the items (you’re really sorting UI elements representing your data), a data binding error occurs for [...]