Hey Steve, this is from the other thread, try this :
Go to the "Preferences..." menu item and click the "Audio" button, then click the "Audio Devices" button.
What do you have set up as an audio device in BIAB ?
Also you could try temporarily setting your MIDI output to "Apple DLS Synth" like Icelander said in the other thread, to see if that helps route MIDI internally to the plug-ins (rather than to an external MIDI port).
This is what I have set as a default in BIAB, and I've never had a problem with instrument plug-ins.
Again, hopefully this helps.
- Jay