[fptex] No room for a new \write + index

[Pascal PERICHON]

Hi,

  To make a book with LaTeX, I need 18 different indexes
(with multind.sty). I use FPTeX version :

 TeX (Web2c 7.3.7) 3.14159
 kpathsea version 3.3.7

and this is a part of the log :

Writing index file droitromain.idx 
Writing index file code.idx 
Writing index file digeste.idx 
Writing index file institutes.idx 
Writing index file novelles.idx 
Writing index file librifeudorum.idx 
Writing index file droitcanonique.idx 
Writing index file decretdegratien.idx 
Writing index file decretalesdegregoire.idx 
Writing index file decretalesdusexte.idx 
Writing index file lois.idx 
! No room for a new \write .
\ch@ck ...\else \errmessage {No room for a new #3}
                                                  \fi 

I modified texmf.cnf and changed the following line
   max_in_open = 15
into
   max_in_open = 30

but no changes... Any ideas ?
(I've got only one texmf.cnf : I verified with "kpsewhich texmf.cnf"
and I recreated all format "fmtutil --all")