Add-Ins no longer appear in "My Add-Ins" when built in Visual Studio

I recently had my operating system (Windows 7) re-installed and now I'm having a problem loading add-ins.

Normally, when I build an add-in project from Visual Studio, the add-in appears in the folder C:\Users\<username>\ArcGIS\AddIns\Desktop10.1

This also used to automatically add the add-in to the "My Add-Ins" category in ArMap's Add-In manager.

But no longer. I have to manually click on the add-in file in the project's bin\Debug folder, or manually point to the folder in the Add-In manager.

How can I get this convenient capability back?

Thanks,
Evan