I ran into an interesting thing with latency when using the Echo button on a vocal track (when tracking). I like to use the Echo so I can utilize a compressor on the vocal on the feedback. However, it seemed that no matter what I tried, I would still experience a minimum 256msec latency. This was after bussing the vocal track directly to the MASTER buss, meanwhile reducing the Recording and playback buffer sizes to less than 256 in both Sonar and on my A/D converter.
 
What I found was something odd. I can set the track output to any other setting, then set it back to the MASTER buss, and voila, the latency was gone! However, if I enable the Echo button on another track, or disable and re-enable it on this track, the latency returns. Repeat the fix in the last sentence, and latency is gone.
 
Has anyone else had this happen?

This has not been resolved. Ignore this post. Merely pressing Record brought back the latency. Also, I fell victim to the Transient Shaper in Sonar again. It's delay compensation requirement is a long time compared to other plug-ins I use.