I was responding to the 2 new posts. I new it was old, I always check the dates. 
 
Epistemoligus,, you should start a new thread, it confuses people as generally we are replying to the OP. 
You can put it in the Main Sonar forum as it's not been determined yet if this is a hardware or a software issue. But first, contact Focusrite, they are very helpful as you'll see the OP found out. 

@Epistemoligus whether you are on the latest version or not. Please try uninstalling mix control, rebooting, and installing the latest version.
 
If the issue persists check if there is a later BIOS for your motherboard (at your computer manufacturers website), and update your chipset drivers.
If it's an Intel motherboard check here for the very latest drivers:
http://www.intel.com/p/en_US/support/detect
 
Also at this stage you might want to check for updates via windows update.
 
If all this fails you might want to try renaming Sonar's AUD.INI file (google for detail).
Then finally give Focusrite in High Wycombe a call...
 
And next time please start a new thread.
 
Thanks..