Solved "sort of" Mixed down stereo levels different on L/R

As it's really difficult to visualise the problem you're having without actually seeing it, can I suggest some steps to take in order to troubleshoot?
 
I had similar problems back in the day with hardware mixers of varying makes, some better than others so I bought a reference test CD so that I could inject signals directly into the various channels for troubleshooting.
 
So how about getting some test signal recordings (wavs) at say 1KHz which should be recorded in mono and dropping them into a channel then bounce to stereo to see if something weird is happening with either your recording, your settings/project or it's an issue with your version of Sonar?
 
I'd also try the same steps using a plain default project from scratch, nothing else added to the project, just open template then immediately follow your process.
 
Over the years I've found that on occasion its been how I had my template set-up, a plug-in or on a very odd occasion, a bug in Sonar!
 
Generally, when I record bass and certain drum sounds, I always do it in mono and leave them that way, only allowing them to drop to stereo when they hit a bus as an example, such as a drum or effect bus.
 
Why would you want to bounce a mono track to stereo?
 
What happens if you leave the recording in mono and just set the interleave in stereo?
 
On occasion I might want to treat a mono signal with a stereo effect and so I leave the recording in mono but set the track interleave to stereo and drop an insert or send effect so that you get a mono signal effected in stereo so I suppose what I'm saying is what are you trying to achieve by doing this?  I have found that with certain recordings, because I can't get them to sound how I imagine them, I've had to be creative in Sonar and come up with an alternative workaround that produces the desired goal.
 
Hope that helps.  :-)

I'm going to do some more with this problem, but as the current project is done (only one I have scheduled until after the 1st of the year) I'll try some older projects that didn't have the problem and see if remixing causes the problem.  I'll report back tomorrow.
 

fireberd
Did some testing this morning with an old project.  Mixes down OK so I have to assume there is something screwed up in the template I used for the demo song project.  However, I've used that same template in the past and no problems.  Murphy's Law has struck!
 
Solved "sort of"
 
Jack

There you go Jack!  That's what I meant when I wrote that I had a similar issue with a MIDI channel.  I isolated it by recreating the same settings on a default built-in template and it worked!  I then went back to my template, deleted the problem channel and recreated it, problem gone!  Never got to the bottom of it.
 
Glad the suggestions helped and you got a resolution. :-)