Garageband 10.0.3: old files won't load instrument plug-ins

Hi all,

I've opened up some old Garageband files in GB 10.0.3 and when I add a new software instrument track, I can't load any instruments. It won't play the apple plug-ins or third-party plug-ins(all up to date). If I create a new project, everything works fine. AU units are selected under preferences.

Here's a screen shot of my load attempt. As you can see, instead of instruments, I'm only seeing effects. Any help with this problem is appreciated.