I'm using some promoted widgets in Designer, but they "disappeared" from the "Promoted Widgets" dialog. However, if I try to add one of the widgets that vanished, the "Promoted Widgets - Error" dialog says "The class [name of the promoted widget] already exists."

In addition, if I select a widget that is indicated to be promoted in the Object Inspector, and right click, "Demote to" isn't in the menu.

Does anyone have an idea what's going on?

Thanks,
Martin