Installing X3e was good advise, thanks. I was on X3d.
But it did not fix the problem.
This kind of thing zaps all of your energy and creativity. It stops you dead in your tracks.
i thought if might be the use of Waves plug ins, but now it is happening on tracks with no effects at all.
I will go ahead and download the Platinum version and install it. I paid for it when it came out, but hesitated since they seem to revise it way too often to maintain stability. May be I'll get lucky.
If not, I suppose I will export all of the tracks as files (or try the OMF export), and then import it back into new projects.
Or just go back to the old days of sound on sound.