The solution that works is to keep using MPI_WORK_COMM in the MPI_ subroutine calls, include mpif.h in the subroutine, but don't try to pass it as an argument or save it in an other integer (as I did under mpich).
Thanks, Jeff, for your help and patience with my stumblings.
Department of Structural and Chemical Biology, Mount Sinai School of Medicine
Voice: (212) 659-5475 Fax: (212) 849-2456
WWW (MSSM home): http://www.mountsinai.org/Find%20A%20Faculty/profile.do?id=0000072500001497192632
WWW (Lab home - software, publications): http://inka.mssm.edu/~mezei
WWW (Department): http://atlas.physbio.mssm.edu