+2  A: 

I've resolved the problem renaming these files:

IconWorkshopAddin.dll      -> IconWorkshopAddin.dll.old
IconWorkshopAddin2005.dll  -> IconWorkshopAddin2005.dll.old

in the program installed folder.

Eduardo Molteni
I also had to run VS as admin to end the infinite "Couldn't find plugin, do you want to remove?" dialog loop.
Ben Straub