Upgrading from Build 2505 to 3400: Add-Ins Disappear from my Display

[JeffAnderson2]

I am upgrading from Build 2505 to 3400.  I built a previous project file and application configuration using 5 AGX Desktop add-ins.  When I use these files with 3400, the add-ins no longer appear in the AGX GUI Add-Ins tab for use.

However, they do show up listed under the ArcGIS Explorer Options Managing Add-Ins GUI:

So what's up here?  I'd like to get my Add-Ins back.  Thanks in advance.