For some inexplicable reason, Unity seems to want me to run Motion Builder and keeps starting it for me (which I really don't want). It seems to do this when I click on any animated object in the hierarchy even though a) I did not animate any of them with Motion Builder and b) I'm not clicking on the animation, only the parent object. I'd really like it to stop doing this. Is there a preference or something I can set? I looked through all the ones I know of. (I'm still using 2.6).
A little late, but I'd expect that you have it configured that Motion Builder is to open all FBX files by default... You'll have to change the settings.
Right click an FBX (Outside of Unity, like, in the windows explorer), and do open with, select a program, choose some other program you want, and click the check box saying open with this always or what not. =)
Why the solution to Unity bug-feature should be to break Windows?