Hello and thank you for any insight into this problem.
Currently my system consists of Windows 10, 64 bit version 1607, SONAR Platinum, AMD FX 6100 processor, ASUS M5A99X EVO motherboard (BIOS as up to date as possible), 8 GB of RAM, Seagate 1 TB hard drive, and my audio interface is a Presonus AudioBox USB. 
 I keep getting a dialogue box that says, "The above Audio/MIDI device was disconnected from your system. Would you like SONAR to reroute these outputs to an available device? Clicking 'No' allows SONAR to remember output settings to this device. Note: If Playback is in progress, clicking 'Yes' will stop playback." The device in question just says "High definition Audio Device". Clicking on either "Yes" or "No" causes the dialogue box to go away for about 30 seconds or so, but doesn't change any settings that I can see. I've had this problem for years and my solution has always been to restart the system, which worked well until to day. When I restarted today, then opened SONAR, the dialogue popped up as soon as the start screen finished loading, before I could open a project. I have all audio devices disabled in Windows except for the AudioBox, which is the only thing showing in the device manager. I've had this problem across different versions of SONAR and Windows as well as hardware changes such as motherboards and hard drives. 
    
 Thanks, Danny

possibly an issue with the connection to the Audiobox (maybe your USB cord) are you plugging your Audiobox in to a USB 2 port ?
 
if it is happening on multiple systems chances are it is the box itself.
Your running you Audiobox with ASIO selected as your driver mode ?

Thank you very much for replying. Yes I'm running the AudioBox in ASIO driver mode. That's what I have (reluctantly) been suspecting is the cause of the problem. It is old and it has never been a blissfully happy marriage between my system, Sonar and the AudioBox. Last year, Presonus instituted a new software management program similar to Cakewalk Command Center, and that has helped keep it stable, but it could still be physical issues with a cable or the USB port. I mainly wanted to check what the possibilities are before I started digging into one specific thing.
Thanks again  

There is some kind of communication issue between Windows and your interface. USB cable or a worn USB port would be the first suspect.
 
However, I get this same message if I forget to turn my interface on prior to booting into Windows. It's as if Windows checks on startup for the device, but is incapable of detecting afterward.

The definition Audio Device is generally associated with an onboard sound card that came with the computer. In some instances it can be also a part of a video card today.
 
If you're not using your onboard sound card you can try disabling it. That should eliminate this.That's not usually a device that comes and goes so that's curious. If a usb device is being being called a high definition audio device, that's even curiouser.

bitflipper
There is some kind of communication issue between Windows and your interface.

bitman
The definition Audio Device is generally associated with an onboard sound card that came with the computer.
 ... If you're not using your onboard sound card you can try disabling it. That should eliminate this.

Both of these ^.
 
I was getting that "High definition Audio Device" error window after a Windows 10 update.
(Not a big fan of Microsoft's new update procedure with Windows 10...)
 
Looking around Device Manager uncovered not one but TWO high definition audio devices - neither of which were my Lynx Aurora. (Look through the chipsets in DM too, as that's where I found an Intel high def audio device.)
 
I disabled them both, and the errors went away.
Audio driver stability also seemed to improve, but maybe that's just me.
 
Let us know what you find,
MG

I get the same message over and over and over and over and over when I try to use Vegas Pro and Sonar running at the same time.   Every time I switch to Vegas, Sonar can't just shut up and stay in the background, it has to complain in your face.    This might be a good feature request: when I've answered that dialog box once, STOP REPEATING IT. 

Thank you all very much for your replies. I fixed it. I went to an MSI motherboard a couple of years ago and it lasted about a year, so when it died, I went back to the ASUS motherboard I originally had in my system. In the mad dash to get back up and running, I either neglected to install the audio drivers for the ASUS board or i did install them and the install was bad. I reinstalled the RealTek drivers, fired up Sonar, fooled around with the project I had been working on for about an hour without any annoying dialogue box, closed everything down and quietly did my best Homer Simpson 'DOH'. 
Thanks again, Danny

bitflipper
...However, I get this same message if I forget to turn my interface on prior to booting into Windows. It's as if Windows checks on startup for the device, but is incapable of detecting afterward.

FWIW, I have an RME Fireface UCX interface and I can turn it ON anytime before I open SONAR (booting up or Win10 up and running) and everything is happy.
 
Walt

Have you checked to see if the "Share Drivers with other programs" option is enabled? You may want to uncheck that box under Preferences/Audio/Playback & Recording