Hi Tom
The first thing that pops into my mind, is the Flash Player security settings.
Usually these only play a role if your buttons are trying to access a internet
address, but sometimes can affect local files also.
Go to you Flash Player security settings (online settings) and add your swf to
the Allow list.
Note.
I don't know how to get to the settings online, it never interested me. But if
you change the link on one of your buttons to access a internet address like
www.google.com, and try to click it from your local machine, the Flash Player
Security screen should pop up and warn you that a "Unsafe Operation" was
stopped, or something along those lines. If you click on the [Settings] button,
it will take you to the online Flash Player settings.
By the way, the Flash Security window does NOT come up from Test Movie. You
need to open the SWF in Flash Player on your local drive.
Hope this helps. Goos luck