What happens if you start Sonar with no project, checking your driver settings independently of any project?
I had trouble with a mismatch on sample rate, and have also had trouble if I was running certain other audio programs (even with the share audio engine button checked).
Does Windows Media Player play audio files properly, outside of Sonar?
Can you start a new project, import an audio file to an audio track, and get that to play?
Bob Bone