Plug-In not seen by Aperture

I have developped several plug-ins for Aperture 3 with the new 4.3 SDK with Xcode 4.6.3 Mountain Lion.

If I install them one at a time in /Library/Application Support/Aperture/Plug-Ins , everything work well.

But, If I install (copy) several of my plug-Ins, only one of them is shown in the Photos/Modify.. menu. All other plug-ins (Nick, etc..) are shown normally.

Any help will be greatly appreciated. Thx