Impossible to add marketing content to a link collection

Description

1. Make sure there is a campaign or promotion instance on the site.
2. Make sure there is a page with a link collection, LinkItemCollection (The start page on the Quicksilver site has two).
3. Go to the page.
4. Try to add a link to the campaign or promotion in the link collection. Either by drag'n'dropping from the campaigns gadget, or by using the create new link dialog.

Expected: The item should be droppable and selectable from the dialog.
Actual: Dropping is grayed out, and there is no option in the dialog to select marketing content.