Can't figure out this divide-by-zero error. Help?

["Owen Davies" <owen@xxxxxxxxxxxxx>]

I've been playing with an oscillator for a while.  Nothing terribly
useful so far, but interesting enough to keep on with for a few
more iterations.  However, I've just tried to write a system that
uses MRO(Oscillator, 50, 1), and it gives me the dreaded
divide-by-zero.  I've confirmed that the error message originates
with the MRO.  I can't figure out why, much less how to write an
anti-DBZ clause to correct the problem.  Does anyone have
any ideas how to cure this?  Where does MRO introduce a
division that could mess up, even when the underlying oscillator
is bullet-proof?

Many thanks.

Owen Davies