When I listen in sonar (x2) I hear the entire mix; when I mix down I'm losing several tracks - I've grouped several tracks into buses to make it easier; as I say everything sounds when I listen through sonar, but when I mix down to stereo, several channels are missing from the mix; I've never had a problem like this before; I'm going to shift to another computer to see if it's the computer but I don't think so it's quite reliable.  For the heck of it I did one try soloing the master track to see if it was a problem with the other buses, but same thing.  Anybody have any idea - as I say, mixdown is usually very dependable  Thanks for help.

so I posted this but not sure if in the right forum - I've got Sonar X2 and I've assigned individual tracks to buses (4); when i'm in Sonar everything comes through fine in the mix - when I mix down to stereo I've got like one bus coming through and not all the time and the others aren't there - I tried to bounce the mix to a track to see if I could do it that way - no - I changed computers and the problem is still there - I've never had a problem with mixdown before and don't see why these buses should sound in sonar just fine but then are not in the mix unless I'm not selecting something I should be - I've thought of an artificial fix, but I'm not happy that the mix is not reflecting what I've got in the file and can't understand why - even when I run a mix with the Master track soloed I still am not getting the tracks assigned to the buses - again they are fine in Sonar, just when I mix down - can't figure it out and would appreciate some insight.  Thanks.

The other post was in the same area a few threads lower. I merged them for you.

if you are running several busses, click on the waveform preview button on the buss.  If something is missing on that buss, then there's your problem.  if it is on the preview, are you sure you are sending that buss to the master buss?  
 
I usually configure 6-8 busses (keys, drums, guitars, vox, fx...) and a master buss that they are routed to.  If you were routed to the main output and not the master buss, you would hear the stuff when you played back but it would not be in the final mix.  

Thanks, Cowboy, good info, I'll check it out and let you know - appreciated - 

I patched them to a new bus (if you mean something else by master bus please let me know) - but same result - I honestly don't know why the buses wouldn't show up in the mix if they are patched to output to the master; but anyway I'm still not getting the buses in the mix; doesn't make sense to me unless I'm supposed to choose an option in mixdown that I'm not choosing - anyway any thoughts are welcome - thanks.

Lets try a hypothetical scenario
You have 2 guitars
A drum kit
A Bass
and a bagpipe
tracks
 
I usually create a buss called "Guitars" over on the almost far right.  I then route my guitar tracks to the guitar buss.  Ditto for drums to drum buss...
 
I create another buss called Master buss  I route Guitar Buss to Master, Drums to Master...(this may seem unnecessary but if you want to glue the mix together using a buss compressor, then you need a comparable arrangement). 
 
If your sound card has say 4 outputs and it is named Larry, then I would send the Master buss output to Larry 1-2.
 
None of the instruments or the busses are sent to Larry 1-2 except Master Buss.   
 
What you hear when you monitor Larry 1-2 should be the same as when you mix down.  
 
Do you have a setup like that?  

This pic is from an old version of sonar, but it helps illustrate what I am saying.  Notice the vertical dividers?
the things called Arp 1 and Arp 2... all the way to the first divider (from left to right) are tracks.  The next 3 are busses (main buss aux 1 aux 2) and after the next divider is the outputs from your sound card.  
 
You want to create busses like in that middle section, then route that to the sound card output.  I like a master because I can mix the various stems more easily in groups.  
 
 

Here is a more recent one showing the same thing.  
 
Left to right.  Tracks to busses to outputs.  They seem to have routed everything to the master (in the center section left) and that is routed to the sound card outputs.  
 

 

When I listen in sonar (x2) I hear the entire mix; when I mix down I'm losing several tracks - I've grouped several tracks into buses to make it easier; as I say everything sounds when I listen through sonar, but when I mix down to stereo, several channels are missing from the mix; 
 
where are the other channels going, if not to a buss? are the missing channels not routed to a buss?