The default driver changing could just be an artifact of upgrades. The View agent installer use to override devices other than what it uses. If your default audio device was Audio Devtap ( What the View Agent Sets it too) you added a third party audio driver, then later upgraded the view agent. It would set the default back to Audio Devtap. We did change this, but I think the issue is other things like VMware Tools now override it.
Although we do not directly test / support all 3rd party components it just means you have to get support / fixes from our partners for their components.
WP