no fish... thanks [blushing with dumbness] apparently that was the case, but it must have happened by accident from some stray misplaced clk... all is happy again... whew... thanks again.
I was on 4.72pre3 when I saw this, but can't see any mention of something which would have fixed this in pre4 Visualisation of envelope points and crossfades is suddenly wobbly! (sometimes) See below (you have to look carefully to see it)