Hey y'all.  So My project is stopping in the middle of playback.  Is this something that sounds like a plugin problem or something else.  TIA.
 

If there is a track starting at the same spot where the playback stops then some vst at that track might be the cause. Just guessing.

Thanks, kakku.  I haven't found that kind of thing but i'm looking.  Thought it was an un-rendered track with V-Vocal on it but that didn't help.I don't mind doing the work of fixing it if i can get some direction, because it is a valuable project. 
 

When i try a mixdown to track, i get 'an internal error has occurred - mixdown has been stopped'.
 
 

So i took advantage of the fact that mix-downs fail on this project.  I mixed down half the tracks, and it mixed down OK - mixed down the other half and it stopped with error - mixed down half of the first half (process of elimination) and it stopped - now down to a quarter of the tracks as the culprit - mixed down half of the half of the first half of tracks and it stopped - down to two tracks, so i tried mix down of one of the tracks and it stopped - so i archived that track and all is well.   I will have to redo the one track, as i couldn't see how to fix it.  It does have a couple of 'reversed' audio clips in it so i suspect this got corrupted at some point.  It was working without issue before.

I am pretty sure that if you select tracks and Bounce to Track(s) from the TV that it does them sequentially, and shows which it is processing at the top. Try saving the project as a new name, select your suspect tracks and Bounce to Track(s). SONAR should hang on the suspect track if this is the issue.
 
This could also potentially be a buffer issue if suddenly a lot of processing engages at this spot in the project. Bumping up the audio buffers may also help.

I've had this problem when I've had a lot of very small edits close together in a project. If it's consistently stopping in the same place, that could be the cause. Bouncing edited clips together usually fixes it.

Thanks all.  It's good to know about the read out of processing for the next time.  Are you referring to the 'playback' 'recording' buffers under the 'file system' in the 'sync and cashing' window, mettelus?

John's point above is a very good one. A "clip" is like a window into the underlying wav file, so you can potentially be telling SONAR to read/process numerous wav files to create the audio stream. When you bounce to clip(s), SONAR creates a new single wav file (embedding any clip FX) which is much simpler to process/stream on your computer.
 
SONAR will never delete the underlying audio on you, only create new ones. If you get a complex series of clips that you may want to edit at some point in the future, it is good practice to save the bounced version with a new project name so you can go back to the previous edit point, bounce again, and pull that audio into the post-bounce project. This is rare to "need" though, as you can always continue to edit from the bounced version.