Interface is definitely stereo, I can pan the main mix.  But panning an individual track has no effect.  I'll continue reading on the 'net but thought I'd put the question in here in parallel as always.
 
CAF

I don't suppose that track is routed via a mono bus?

The tracks are assigned to Master which is a stereo bus and I see the two level bars on Master, shifting pan on master changes those bars and changes the audio output.
 
None of my audio tracks seem to be panning.  For instance, on a stereo track I see the two level bars on the track but pan does not affect nor is there any change in audio.
 
CAF

Loaded the project in 32 bit SONAR as I've had issues with other stuff not working in 64 bit (the AudioSnap stuff) but that made no difference altho the Dimension Pro of course didn't load.

I can reproduce this if the master bus interleave is set to mono (which of course it shouldn't be).

Assigning a track directly to the audio interface makes panning work.  So it's like my master buss is mono-ifying things.  I took the multiband off the master thinking maybe that was the culprit.  Nope.
 
Huh, adding a new stereo bus gets me back to stereo.  It's looking like I need to delete my Master and make a new Master.  Anyone seen this before?  Any secret setting on a bus I'm missing?  I don't think I've touched anything but you never know what stray keystroke shortcut might have done something mysterious.
 
CAF

Tried changing interleave, no change.  Thanks for the help.  Making a new master bus now I guess.

Made a new bus.  Everything sounds much better now and pan works.  Huh, not sure how the old Master got sick... but back to making music now.  Thanks.
 
CAF

ChewingAluminumFoil
Assigning a track directly to the audio interface makes panning work.  So it's like my master buss is mono-ifying things.  I took the multiband off the master thinking maybe that was the culprit.  Nope.
 
Huh, adding a new stereo bus gets me back to stereo.  It's looking like I need to delete my Master and make a new Master.  Anyone seen this before?  Any secret setting on a bus I'm missing?  I don't think I've touched anything but you never know what stray keystroke shortcut might have done something mysterious.
 
CAF

Yes - It has happened to me, and not just on the Master bus. I think my problem happens when I use a project template (which has most of the buses are already panned). I tried everything I could think of, but the only solution I hit upon was the same as yours...Make a new bus and move everything over to that.

I have had this happen many times. I came to the same conclusion as you.... replace the bus.