Denis, Laurent,

I've not figured out why this problem is occurring. But I am not
totally surprised that it _does_ happen, because the code for handling
.mar files has become too complicated. There could be dozens of bugs
lurking in it.

I've started work on something I should have done a while back: I
am rewriting some of the worst parts of the 'marks.nam' (and
'overlays.nam') code so that their logic will be... well, logical. I
think that will probably cause the bug you found, and probably many
that we've not found, to vanish.

Thanks! -- Bill