I wrote:
The solution is to enter an appropriate "guess" (last IRR
argument) other than 10%. Unfortunately, there is no guidance
about what is "appropriate". In another thread, I believe
someone suggested that -10% (or was it -0.1%?) always(?)
works. I am probably wrong about those details. Search for
the thread.

I found it. In another thread in m.p.e.worksheet.functions,
Harlan Grove (11/4/2005 3:19p PST) suggests using -0.9 (-90%).