I pinned Windows Explorer's icon to my taskbar months ago, and all worked fine, including jump lists. Note: I changed the default Explorer's folder using the usual trick of changing the GUID in the shortcut.

Now, all of a sudden, the jump list is empty, and dropping folders on the pinned icon does not produce any effect, nor recently-opened folders show up in the list (although in the taskbar options I made sure to have it remember recently open items).

How can I restore the original functionality, given that all other pinned applications jump lists work correctly?

I'm running Windows 7 Ultimate x64, updated with the latest patches. The OS is in US English and my locale is Italian-Italy.