Having a bizarre issue. I already had the issue where R-Mix causes midi notes to drop out, the forum helped fix that by changing my buffer to 512 milliseconds. The issue I have now is after I press play, or record, if I play a note with my MIDI Controller (Roland XP-30) there is suddenly a latency/delay of about half a second after each pressing of a key. No drop outs, just latency/delay. What's more, if I open the project, it works fine until I press play or record. Also, if I simply open Preferences, and click Apply (without even making changes) it suddenly works fine again, until pressing play or record. Any thoughts? Searched the forum and found nothing, it all relates to the drop out issue. Thanks a ton!

Latency is caused by audio interface settings and plug-ins that have to buffer input. If you can, lower your audio interface buffer settings. Disable all plug-ins for a general solution or individually to see which one is causing the delay. The usual suspects included with SONAR are LP-64 EQ, LP-64 MultiBand and Perfect Space.

You can disable effects by hitting 'E' on your computer keyboard, check to see if that gets rid of the latency or not, then start looking at each plugin effect to see which one(s) is/are causing the issue - if bypassing the plugins did in fact get rid of the latency.
 
Hitting 'E' again would toggle effects back on.
 
The above is independent of also checking out the settings on your audio interface, and driver mode in Sonar, as pointed out by the other poster.
 
Bob Bone
 

Alrighty, I tried bypassing effects and found that it is R-Mix. Is this the only way to record new MIDI is by bypassing R-Mix in other tracks each time? if so im glad there is at least a solution, just seems a little bit much :/

Yes, there are several latency inducing plug-ins that are not intended for use during tracking. R-Mix falls in that category.

Several of the plugins are meant for use in mixing/mastering, due to the nature of the plugs themselves.
 
I do not know what the complete list of the plugs that cause tracking problems are, BUT the approach to living through it is pretty straight forward.
 
Just find one of the non-latency inducing plugs to use during tracking, for example one of the more benign reverbs than Perfect Space, then after finishing the tracking, swap out the generic reverb for the more robust Perfect Space, etc.
 
Once you have the list of what you need to beware of, during recording, you really have only the swapping to do for mixing and then on to mastering.
 
Bob Bone