This issue will occur when certain USB audio devices which do not have a software mixer are connected. While there are a number of USB audio devices that may cause this to occur, we have confirmed this behavior with the following devices:
- Yamaha RP-U100 CAVIT External Audio Soundboard
- Yamaha AP-U70 CAVIT External Audio Soundboard with Integrated Amplifier
- Yamaha RP-U100 Receiver
- Edirol UA5 Audio Interface
In order to resolve this issue you will need to physically disconnect any USB audio devices you may have connected. If you are using a USB audio device as your primary soundcard, you may need to remove this and replace it with a PCI soundcard or enable your onboard soundcard if one exists.