Can you please tell me what sort of audio interface you are using in Sonar? Is it an actual device, like a dedicated external audio interface, or are you using your computer's on-board sound chip, or perhaps ASIO4ALL?
Also, if you open Sonar and go to Preferences, which you can do by going to Edit>Preferences up at the top of the Sonar screen, or you can simply hit the shortcut, which is to hit the letter 'P' on your computer keyboard.
Once in Preferences, under the Audio section, what is showing under Devices as being checked to function as your audio interface?
Once we figure out the above, I will have a few more questions for you, and I will keep a lookout for your reply with the info I am requesting. :)
Bob Bone