I'm using Sonar X3 Producer which I bought in 2013. OS is Windows 7.
 
recently I frequently have the same problem: When recording tracks there is sometimes a latency of ca 1/4 of a second between playing and recording. This problems occurd with acoustic recordings and also with Plg in synth (I use True Piano's a lot).
The problem is imo in the recording because I can see on the screen that the signal from the mic or the synth is also later than that it is played. There is no time difference between the VU-meters on the screen and the output.
 
Funny is that if I copy all previous tracks to a new project this problem does not occur.
 
I hope that there is a better solution to this problem than what I have found until now.

In cases like this the audio interface can be the culprit. It uses buffers to store data and then use it. Think of it like a water heater. It holds the data and then uses it so the software doesn't stall. The smaller the buffer the less the latency. This is dependent on the capability of the computer, the software drivers and the computer.
 
If the computer isn't up to the task, simply record both a midi and an audio track without the soft synth. Then add the midi to the soft synth. You can use the audio track to line up the printed midi track if necessary.
 
Another thing to check is the monitoring of your interface. If you can't directly monitor try to record with the monitor button disengaged. Guitar can usually be heard without the need to monitor it. Have more than a few channels on your interface? Go into the interface front end and disengage all unused channels. This will make things slightly faster. Good Luck!
 
If none of that works come back round' and we'll see what else can be done.

You should only use ASIO mode with your audio interface. If you do not have one, get one of forget recording in sync. Audio drivers are the most important part of a Computer based recording system.