Hi all, I have a rather weird situation happening to me.
 
I've been working on a project for the past month and have been able to record my guitar with very low latency.  One day, I tried to add Melodyne to my project and it complained about buffer size, etc.  I tried to work with the preferences to increase buffer size by switching to WDM/KS.  But the system seized for some reason and, when I got it back, I suddenly have like a 1/4 second or so latency when playing.  There's obviously no way to do tracking like this.
 
I've switched back to ASIO and the calculated latency is now 7 ms which is totally acceptable but, when I play the guitar, the actual latency between hitting the string and the sound coming through is still around a 1/4 second.  The ASIO Control panel meters show an immediate response but the Sonar 10 track meters show the delay.
 
Now, here's the weird part.  If I open another project I have with the same Audio Input, same settings, there is virtually no latency.  If I switch back to the first project, the latency returns so this is project-specific somehow.  I've compared all settings under drivers and am using the same settings on my ASIO Control Panel.
 
Any ideas would be greatly appreciated.

If keyboard shortcut E or clicking the FX button in the Mix module gets rid of the latency, the problem is plug-in related. The PDC button in the Mix module may help, see http://www.cakewalk.com/Documentation?product=SONAR&language=3&help=Recording.22.html
 

The PDC button did the trick.
 
Thank you so much!! 
 

But this wasn't a problem before and it's not a problem on the other project.  If I manually bypass all of the plugins, the latency is still there.  There has to be something that is "stuck" between my interface and the project.

Try toggling the PDC setting after bypassing the plug-ins.

Just two cents... I had a latency issues about the same. For me it was the difference was Direct out to the audio interface = no latency and going through a Aux or buss = latency.
:)  

Bypassing plugins does not remove PDC. PDC is preserved so that any plugin can be bypassed and then unbypassed in real time without causing audible timing hiccups. Without removing the delay-inducing plugin, only the PDC button can remove PDC.
 
There is more info in the link in scook's post. Look for some particular plugin in your project that requires automatic plugin delay compensation.