I have been using X1 on and off for several months without any major problems.  But just today, X1 fails to recognize my Scarlett 8i6 Focurite interface and I can’t figure out why. 

• When I open an X1 project, I get the error message “Silent Buses Detected” and Master is listed as the silent bus.
• The output from my Master bus has changed to “None” and selecting any Focusrite options available don’t produce any sound, and they don’t appear to be the correct options anyway.
• If I go to any audio track, the Input has changed to “None” and I cannot find and select the correct Focusrite input, e.g. “Left Focusrite USB Driver Mic 1” no longer exists.
• The physical connections between my PC and my Scarlett 8i6 seem fine and has not changed since it was working just fine the night before.
• Under Edit > Preferences > Audio > Devices, the input and output drivers appear to be correct (although I cannot be sure) and they are all checked
• My Scarlett 8i6 appears to be working fine otherwise, e.g. if I play an mp3 from my computer which inputs to my 8i6, the sound is fine.

 
Any suggestions appreciated!  Thanks.  - Greg

You've tried a different USB port and hard rebooting your computer (power down, wait a bit and restart)?

Make sure you are running X1D.
Whether you are running the latest mix control or not try uninstalling mix control and reboot.
 
Then install the latest here and configure mix control:
http://uk.focusrite.com/usb-audio-interfaces/scarlett-8i6/downloads
 
Also try renaming AUD.INI in Sonar (google for details on how to do this).
 
Thanks..

Thanks.  I'll give these a try and get back to you.  -Greg

By playing an mp3 you can have that steal your audio drivers. Double check your in ASIO mode and not MME. Every system seems to handle this differently and there is different configurations that will work for one person and not another. 
I disable my on board audio completely. I check share drivers.  This works for me. It's simple and I only need the one system for everything. 
Others use the on board to play Windows sounds and  MP3 and un check share drivers. This involves having the mobo audio output connected to something. You can run the audio out back to your interface or better yet a small mixer you use for this. 
Try them both.  
First check that Sonar is using ASIO mode. 
 

I’m still having the same problems.  I restarted my PC many times, changed the USB port, and I installed the latest Scarlett 8i6 mix control (per above link), but I HAVE NOT YET TRIED the following yet because my technical knowledge is not that great and I could use some specific instructions:

1. I have not uninstalled the Scarlett mix control because I’m not sure what to do.  If I go to “Uninstall or change a program” in my PC, I see “Focusrite USB 2.0 Audio Driver 2.5.1” that I just downloaded and installed.  Should I uninstall it anyway and reboot?  Or should I uninstall it, reinstall the new one again and reboot? 
2. I cannot find the AUD.INI file.  I assume someone can give me the path and I just need to navigate to it and change the file name, right?
3. I’m not sure how to try the troubleshooting steps suggested by Cactus Music above.  Under Preferences > Audio > Playback and Recording, the driver mode continues to be ASIO.  So not sure what else I should do.  Again, Sonar X1 and Scarlett were working and configured just fine for me (for over a year) and then suddenly, BOOM, this problem happened.

 
Thanks.  Greg

1) Yes. Uninstall and reinstall regardless.
2) Google 'rename AUD.INI' for more details. Search your hard drive as well.

X1D?

Thanks...

Here's how to find aud.ini:
 
http://www.cakewalk.com/Documentation?product=SONAR%20X2&language=3&help=INI_Files.6.html
 
 

Thanks but am still confused on "renaming the aud.ini file” (despite Google search).   I followed the instructions for FINDING the aud.ini file (thanks Ian Ferrin) by opening it up within Sonar.  But this only allows me to editing what is IN the aud.ini file, NOT RENAMING the file name (I assume).  In the meantime, I found my aud.ini file within Windows:   Users > (my name) > AppData > Roaming > Cakewalk > Sonar x1 Producer.  Within that folder can I simply change the name of the “aud.ini” file to something like “aud.ini-old”? 

 
Thanks.  - Greg

yes