I'm using Sonar X3, or 3X, whatever... and an Akai MPK261 controller... I only get audio sporadically and it seems to be tied into whether I'm in play or not. In play (on Sonar) I can play along and hear my chosen midi instrument, as soon as I hit record I can no longer hear the tone, but it has recorded the midi info because it plays back, I just can't hear it while recording. And I can only hear it in 'stop' sporadically. Also, when I can hear it, after a few seconds of play the sound will either stop altogether, or a note will begin to sustain and I have to stop the program to stop the note, then I no longer hear output from the controller.

Please provide the following:
 
1. Computer make/model or CPU, OS and maintenance level, memory
2. Type of sound output from computer - (on-board or dedicated audio interface - if interface then model)
3.  Sample rate of sound device 
4.  Sonar Driver Mode and Sample Rate
5.  If external interface - is it connected through Fire Wire?  USB?
6.  If USB - are you plugged into USB 2 or USB 3 into computer, with the interface
7.  If your project has effects loaded, does the problem go away if you temporarily bypass all effects, by hitting the letter 'E' on your computer keyboard?  (hitting 'E' again will turn the effects back on, by the way).
 
We need more info than you provided - I do not know if any of the above are factors in your issues, but it is a place to start.
 
It is also possible your midi buffers in Sonar are too small.
 
Lots of folks post their computer specs in their signatures - you can look at the bottom of my post for an idea of what someone might list - it helps others in the forum understand your system at a glance when helping you - for this or for future issues you might have.  To add info to your signature - click on User Control Panel, then on the Signature button, and add your info, making sure to also check the box that says:'always attach signature to post' and then save the info.
 
It is hopefully something simple, like increasing your midi buffers, etc.
 
Bob Bone
 

No make or model, self built, Windows 7 SP1, AMD Athlon II X4 640 3.00Ghz 64bit

Presonus Audiobox USB

44.1khz

ASIO 44100

USB2

I had a reverb on an earlier track but I've removed and it did not affect the issue

Be sure you have echo on on tracks you want to hear as you play a controller. 
 
Its X3!

Could very well be the MIDI buffer setting. Try increasing to 500 or 750. It's in Preferences under MIDI > Playback and Recording.

Nothing guys... checked all this... I was playing, recording, didn't change any settings that I know of but I have no out put... I have one track with a short drum part for which I can see the meter moving when it plays but I cannot hear it, the other tracks don't seem to affect the meter though the info is there.

Have you checked your routing of your midi track to your audio track to your output?  Anything muted?

sorry guys, I was stressing about midi so much and stuck in one file, I didn't realize that suddenly I'm getting no audio output from Sonar at all, not even my audio tracks, so I'm trying to track that down before getting back to pulling my hair out over midi. *sigh* I'll take any suggestions in that regard as well.

Check Bob Bone's post above and provide the requested info.  This forum will get you sorted in no time, but they that info to help.
 
Also, can you play itunes or windows media player and get sound?

I did, in the very next post. Did I miss something?