We had a similar problem when I tried to load the add-in onto my students machines. We don't give them privaleges to install so I get the honor. After several false starts here is the easiest way to get it to work:
1) sign in as admin and install (That creates among other things, the C:\Program Files\Microsoft Research sub-directory which is important)
2)Change permissions on the Microsoft Research directory to allow all users to write to it.
3) Then the student also install it and then it works.
I'll let the developers explain why, if that is necessary. I am just glad it works!