The soundcard probably really is in use by some software you may or may not even uses the soundcard all the time. Such as something running in the system tray. Sometimes they can give feedback through sounds (like when a drive is finished defragging, or a cd is done burning, etc)
Try closing everything in your system tray. Then re-try Breakaway.
If not, then open your task manager and start closing things that are not "standard" windows processes. You might have to look up the ones you don’t recognize as being standard processes on the web to see what they are. Then re-try Breakaway.
If all else fails and you don’t mind a bit of added latency, you can always try DirectSound (DS) or MME (Wave), which don’t require sole access of the soundcard device.