I have more info:
Generally when I do additional work I do a SAVE AS then SONG--TK01, SONG-TK02, etc.
That's when it locks up. On a straight SAVE (overwriting the file using the same file name) I have no issues.
I've never had this issue before.
Added: It does not lock up the entire PC just Sonar. I have to kill Sonar using the Task Manager and Sonar will not re-load unless I reboot.