Setup

Since this is now your default audio device for Windows playback and recording, WITHOUT Sonar running, do song files play properly on your system, using something like Windows Media Player?  If not, then there is something amiss outside of Sonar.
 
Please try the above and post back the results.
 
Bob Bone
 

Well, since it plays outside of Sonar, through your interface, it is likely the Sonar Preferences that need some tweaking for your interface.
 
Please go into the setup screen for your audio interface and post back the Sample Rate and the ASIO Buffer Size.  (ASIO Buffer Size is sometimes set with a slider - if so it might be listed as something like 'number of milliseconds').
 
(My recommendation for a reasonable starting point for your interface would be a Sample Rate of either 44.1k or 48k, and an ASIO Buffer Size of 128 - or if expressed in milliseconds, shoot for somewhere at or slightly less than 11 milliseconds).
 
Once those values are set, power off the interface and power it back on.  All of this should so far be done with Sonar not running, if possible.  Some interfaces only allow access to their control panel settings by going through a host application, in which case you would have to hit the ASIO Control Panel button in Sonar Preferences, then make your changes, then erxit out of everything and then power off/on the audio interface.
 
OK, now that the above is done, go into Sonar's Preferences>Playback and Recording, and make sure that you have a Driver Mode of ASIO specified.  If you had to change it to be ASIO, then click Apply. 
 
Now, go to Preferences>Audio>Driver Settings and make sure the Sample Rate EXACTLY matches what you set it to in the control panel for your audio interface.  Click Apply.
 
Now, go to Preferences>File>Audio Data, and tell it to use a Record Bit Depth of 24 bits, then click Apply.
 
OK, now start up a new project, use the Normal Template, and import a song file from your computer (WMA or MP3) into a new empty audio track.  You may have to insert an audio track - I don't remember what the default Normal template has or doesn't have in it.  Once Sonar finishes importing the song file, hit Play, and post back on whether or not you are getting sound, AND if it sounds clear with no dropouts or crackly noises.
 
If it plays back OK, then you are all set.  If not, well...... Then we have some more work to do.
 
Bob Bone