We’ve found that our UR28M literally shuts down our New Mac Pro. We have the latest firmware/drivers for the UR28M and are running OS 10.9.5. It only happens when the UR28M is powered on. It doesn’t happen immediately - it can happen within 5 minutes or 5 hours - but it will always happen. This does not happen when the UR28M is off. Any thoughts? Thanks.
That is certainly odd behavior. The latest USB-audio driver is supported for 10.9 Mavericks.
I recommend you uninstall the Yamaha USB-audio driver from your Mac, restart your Mac, then install the latest driver version from the page below, restart your Mac again, and then see if the issue persists. Perhaps removing the driver and reinstalling with the newest version will resolve the issue.