Non-Stop Error Message in SONAR 8.5.3 PE Regarding Audio/MIDI Device Not Connected.

Was it working before?
Is that your only audio card or is there another device?

Well my friend you are among the millions who always end up getting the same advice. You will have problems trying to use Sonar with on board sound. It is recommended to purchase a interface , USB are the most common. I'm suprised you didn't read the many other many threads on this topic. ( also that I beat CJ ) 

I have exactly the same problem with my laptop. I believe it is a bug in SONAR that crept in when they added features for automatically dealing with device changes. Something is occurring with the Conexant driver that is making SONAR think it's been disconnected. A google search indicated that this is a widespread problem, not just with SONAR.

Nevertheless, I still believe there is a bug in SONAR because I also get annoying messages whenever I change the ASIO buffer sizes or switch between clock sources on my primary DAW. These began at 8.5, I think. If I merely change the buffer size, SONAR pops up with "MOTU Audio Wave...The above Audio/MIDI device was connected to your system. Do you want SONAR to add this device now?" SONAR has misinterpreted some event as the interface being physically disconnected.

And please, don't anybody tell me that the integrated audio is crap and suggest a USB device to replace it. That's really not an option on a 12" tray table at 30,000 feet, which is where I usually use the laptop with SONAR.

Sorry, I guess I'm out of line trying to give advice here. I leave quietly .

No, don't leave on my account, Johnny! Your advice is sound. Anyone looking to do serious recording will eventually want to upgrade to something better than their built-in Conexant or RealTek interfaces, which are really only suitable for gaming and such. But everybody has to start somewhere, and crap integrated audio ought to work well enough for someone to get their feet wet.

I don't know if anybody ever responded with a viable answer to this and since I had the EXACT SAME problem, I thought I would toss out my answer.
 
I'm still not exactly sure WHY it happens, although I believe it has something to do with that useless Conexant SmartAudio app that loads with the driver, trying to take exclusive control while sonar is using it.  So.....
 
With that in mind, I uninstalled the Conexant Pro Audio Device from Add/Remove Programs in control panel.  (which, of course, uninstalls the sound driver, but, also uninstalls that SmartAudio control app)
 
Then,
Instead of reinstalling the software, I just right click on "Computer", goto properties, device manager and search for changes...  The sound card will then pop back into the device list, with a yellow exclamation point.  then,  you just right click and re-install the drivers by doing it "automatically" and allowing it to search online for the driver.  Once the driver is installed, the sound card will work perfect with windows again, but, you will be minus that useless SmartAudio app that comes with it,  and....  you will also be rid of the annoying pop up in sonar.
 
so...
 
As long as  you can live without that useless SmartAudio app....
 
there it is. 
Good luck!