Sorry for taking everyone's time.  I truly believe there is something fundamentally wrong with my system as I have lots of bugs no one else does.
 
This happened with the dedicated scissors tool on audio clips.  I routinely split clips.  Just for one example, I cut all harmony voices to start and end at the same time to make it easier to copy them into other choruses, or to reverse parts for Chorus 1 and 2 on different tracks to create doubling (or tripling).
 
In this case, I was slicing up an audio clip into small parts and muting them one at a time to find a click (pop) I wanted to eliminate.  This worked on a previous clip.  I sliced a very small section of a harmony voice and muted it.  The very noticeable click went away.
 
These clicks resulted from bouncing Melodyne.
 
By the way, I am going to re-record these voices.

Have you tried turning off the Snap To/By feature? Sometimes if I'm zoomed in and try to split with it ON, I can't see the split because it split where the Snap told it to instead of where my cursor was.
 
Also, try Bouncing that particular clip, then try splitting again.
 
Steve

I am here investigating that very same issue - to clarify once more - I was just working on the very same audio track - at different points in the song... splitting using the shortcut "S".  Sopying one part of a guitar take by splitting out one measure... copying it to a later point in the song.  Split at beginning of measure, then beginning of next measure.  Copy - Paste - all of a sudden.... s doesnt work anymore and Ive never been able to figure out why - its not the first time.  Its not that I have automation lanes etc... its none of the things mentioned here.... it just... quits...  it actually appears to be "saving" as if I am hitting control s....?
 
Also - in copy and paste world - one very annoying thing that I experience when working in this fashion... is it seems like it should be a no brainer that when I copy a measure from one track - that it default to paste it to the same track... or at least open the menu as soon as I hit control c...
 
x3 producer - very experienced user
 

I have seen the same issue several times. Rebooting SONAR is the only way to get splitting work again.
SONAR X3 Producer x64 here.

Hi Gang...

Yes, I too have had this happen but I always made myself believe it was something I did without knowing...

I was only able to correct the issue with a Sonar reboot as Konradh mentions...

So it appears something is going on here as more chime in with witnessings... (Is that a word?)

Keni

Sounds to me like a maxed out buffer..... Somewhere!!

Good to know I'm not alone.

I have seen the case where I can't turn the split tool of when changing between projects using alt+w. I have to close and reopen to fix it. I wonder if the two are related.

I'll add one more confirmation. This has happened to me, as well. No take lanes open or anything like that. Just splitting away, and suddenly it stops working until I restart SONAR. I can't say that it's happened with Platinum, but I'm not absolutely sure.

 I have had this happen quite a few times. Restarting Sonar is my go-to workaround. At least I now know I am not alone:)