Update:  I re-posted this in 'Get Started'.  Found threads here, and at M-Audio's site, with same problem...reading and researching.
 
Happy Friday!  I recently got some help in Hardware Forum and it turns out I was using the ASIO4ALL driver - which I didn't remember downloading a while back - oops.  Anway, have ASIO installed and selected in Preferences now.
 
However, from within Sonar, if I select ASIO Panel and attempt to change the latency in M-Audio's Control window, which pops up, this error message displays...
 
'Fast Track Pro Panel'
 
"An invalid operation was attempted on an active network connection."
 
...and the latency cannot be changed.
 
If I close Sonar and then open M-Audio's Control, I can change the latency, but anything less than 512k samples results in stuttered playback with clicks-n-pops, etc.
 
So, within Sonar the latency slider and buffer size box are greyed out and the ASIO Panel button is active.  But, there is another place within Preferences where you can select a driver.  It's under Audio>Sync and Caching - 'Record Latency Adjustment (samples)'  That is currently set to 'ASIO4ALL v2 (1 in, 1, out)', but when I select the only other option,  'M-Audio USB ASIO (2 in, 2 out)' and Apply, it always defaults back to the ASIO4ALL option.
 
Anyone familiar with this?  Wrong forum?